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\begin{document}
\begin{center}
{\Large\bf
Semi-productive polysemy and sense extension}\\
{\large Ann Copestake}\\(University of Cambridge Computer Laboratory,\\
University of Stuttgart and CSLI)\\ {\large Ted Briscoe}\\ 
(University of Cambridge Computer Laboratory\\ and
Rank Xerox Research Laboratory, Grenoble)
\footnote{We would like to thank Geoff Nunberg for many helpful
comments on a draft version of this paper, much discussion and several
examples.    
We have also benefited from the discussion at presentations of
earlier versions of this paper at the Dagstuhl seminar on `Universals
in the Lexicon' (March, 1993) and at the CSLI workshop on `Ambiguity
and Underrepresentation' (September 1993).  We thank two anonymous
referees for their helpful comments and suggestions.  We take full
responsibility for any remaining errors and infelicities.  This work
was partly supported by the ESPRIT Acquilex-II, project BR-7315, grant to
Cambridge University.  We would also like to express our gratitude to
Xerox PARC for providing Ann Copestake with a pleasant and productive
working environment while this paper was being written.}
\end{center}

\section*{Abstract}

In this paper we discuss various aspects of systematic or conventional
polysemy and their formal treatment within an implemented constraint
based approach to linguistic representation.  We distinguish between
two classes of systematic polysemy: constructional polysemy, where a
single sense assigned to a lexical entry is contextually specialised,
and sense extension, which predictably relates two or more senses.
Formally the first case is treated as instantiation of an
underspecified lexical entry and the second by use of lexical rules.
The problems of distinguishing between these two classes are discussed
in detail.  We illustrate how lexical rules can be used both to relate
fully conventionalised senses and also applied productively to
recognise novel usages and how this process can be controlled to
account for semi-productivity by utilising probabilities.

\section{Introduction}

Discussion of polysemy has been central to much recent work on lexical
semantics.  Most of the arguments for (or against) attempting a
fine-grained classification of semantic structure in the lexicon rest
on the treatment of polysemic behaviour and attendant syntactic
effects.  In this paper, we argue for a distinction between two
classes of systematic polysemy: constructional polysemy, where a
single sense assigned to a lexical entry is contextually specialised,
and sense extension, which predictably relates two or more senses. We
present a unification based formalisation and implementation in which
the former is treated as instantiation of an underspecified lexical
entry and the latter as a rule-governed relation between signs.

It is important to distinguish putatively systematic or conventional
polysemy from homonymy or unsystematic and idiosyncratic
polysemy;\footnote{We use `conventional' to refer to a sense which is
accepted and well-attested within a speech community; sometimes this
is called `institutionalised' (e.g.~Bauer, 1983:48) or `established'
(e.g.  Cruse, 1986:68).}  the two familiar senses of {\it bank} as
`financial institution' and `raised earth' are homonyms, whilst the
verbal sense meaning to `put money in a bank' is polysemous with the
nominal financial institution sense. It seems plausible that this case
of polysemy is an example of a systematic sense extension by which
nouns denoting artifacts become verbs denoting a purpose to which
those artifacts can be put (e.g.~{\it button}, {\it hammer}, {\it
butter}, {\it waltz}, and so forth); though, of course, such claims
need to be carefully argued for each such case.\footnote{See Clark and
Clark (1979) and Hale and Keyser (1993) for two widely differing views
of such denominal verbs.} In what follows, we will be concerned only
with cases of putatively systematic polysemy and sense extension which
extend to semantically-defined classes of lexical items. 

Some work on systematic polysemy has emphasised the conceptual or
cognitive nature of the transfers or mappings which underlie such
processes (e.g.~Nunberg, 1978; 1979; Lakoff and Johnson, 1980;
Fauconnier, 1985; Martin, 1990). This work is important in mapping out
the range of possible conceptual transfers available and also
motivating their existence.  However, alone it cannot account for all
aspects of of the linguistic phenomena. Other work has emphasised more
the conventional nature of certain transfer processes (e.g.~Apresjan,
1973; Ostler and Atkins, 1992), their similarity to derivational
morphological rules (e.g.~Copestake and Briscoe, 1992), and
cross-linguistic differences in their patterns of realisation and
conventionalisation (e.g.~Nunberg and Zaenen, 1992).  Still further
work has emphasised the intricate connection between polysemy (or
paradigmatic change) and associated syntagmatic effects, for example
on argument structure (e.g.~Levin, 1993), and the possibility of
characterising some apparent polysemy as a product of syntagmatic
combination (e.g.~Pustejovsky, 1991, 1993).

Sense change or extension accompanies many if not most operations in
the lexicon, including those familiar from derivational morphology,
many grammatical function changing operations, and so forth. Some have
been extensively studied, though usually more from the perspective of
the morphological or syntactic consequences of such operations. In
what follows, we will focus on processes of conversion or
zero-derivation and particularly on processes which do not affect the
major category status of the modified word. One reason for this
restriction is that there is a consensus that morphological processes
involving explicit affixation are rule-governed, and increasingly the
focus of discussion of such examples is on their semantic effects
(e.g.~Riehemann, 1993); on the other hand, processes of conversion
with minor or no grammatical corollaries have a more controversial
status, and the need to treat these as rule-governed requires more
careful argumentation. Furthermore, even if we can show that such
processes can be systematic it remains to demonstrate that systematic
polysemy is achieved via operations analogous to morphological
rules. In this paper, we argue that processes of both sense modulation
and sense change (see e.g.~Cruse, 1986:50f) play a
role in accounting for systematic polysemies.  We attempt to
distinguish modulation from change using tests traditionally
associated with the distinction between vagueness and ambiguity and
relate this to the formal representation.\footnote{The term
`vagueness' has been used to refer to more general less specified
senses, such as the `humankind' sense of {\it man}, as opposed to the
fuzzy peripheral denotation of {\it cup} or {\it game}. Cruse
(1986:81) argues that `generality' would be more appropriate to the
former. We continue to use `vague' to mean general or unspecified in
deference to existing usage. The distinction between sense modulation
and sense change is similar to Bierwisch's (1982) distinction between
conceptual shift and conceptual specification.}

Many types of conversion process are recognised as paralleling
analogous processes of derivation or compounding, and thus treated as
rule governed cases of `zero-derivation'; for example, it is
uncontroversial to suggest that a noun such as {\it purchase} is
deverbal and ambiguous between eventive and resultative readings in
the same manner as the morphologically complex {\it replacement}, and
to propose that the lexical rule which forms deverbal nouns should
cover both cases. Similarly, Hale and Keyser (1993) propose that the
process of noun incorporation which forms denominal verbs in examples
such as {\it babysit} (e.g.~Baker, 1988) be generalised to account for
`total incorporations', that is, conversions, of the form {\it
shelve} (from {\it shelf}), {\it calve} (from {\it calf}), and so
forth. Likewise, Levin (1993) lists many verbal diathesis alternations
which are usually treated as rule-governed conversions because
of their clear affects on argument structure (e.g.
causative-inchoative {\it He broke the glass} / {\it The glass broke}).

By contrast, apparently systematic polysemy or sense extension which
at most involves subtle grammatical changes, such as various types of
nominal metonymy, are often explicated in terms of processes of
conceptual transfer or mapping (e.g.~Lakoff, 1987), and are usually
treated as essentially pragmatic phenomena (e.g.~ Nunberg,
1979). However, some nominal metonymies have closely-related
derivational counterparts; for example, the conventional metonymy
which allows a container to stand for its contents ({\it He drank a
whole bottle (of whiskey)}) is paralleled by suffixation with {\it
-ful} ({\it He drank a (?whole) bottleful (of whiskey)}).\footnote{The
semantics of these two processes are not identical: {\it -ful}
suffixation has an additional entailment of fullness or completeness
which accounts for the preferred usage of {\it -ful} nominals as
measure phrases (e.g.~{\it A spoon / spoonful of sugar} in a recipe
context). Such differences are expected given blocking / preemption by
synonymy (e.g.~Aronoff, 1976; \S6 and below).} Cross-linguistically,
metonymies which involve no syntactic change in English can involve
systematic changes in other languages; for example, the conventional
nominal metonymy by which a fruit or nut denotes the tree of the fruit
or nut (e.g.~{\it apple}, {\it chestnut}) is normally accompanied by a
change of gender (masculine tree) in Spanish (e.g.~{\it
aceituna/aceituno} (olive) or {\it pomela/pomelo} (grapefruit)) and
Italian (Soler and Marti, 1993). Whilst the underlying explanation for
the possibility of such processes may rest on a cognitive account of
conceptual transfer (Lakoff and Johnson, 1980; Lakoff, 1987) and/or a
general pragmatic account of the `cue-validity' of different metonymic
functions (Nunberg, 1979), these cross-linguistic differences and the
similarities to other rule-governed lexical processes suggest that the
pragmatic account must be overlaid with an account of lexical licenses
(Nunberg and Zaenen, 1992) or lexical rules (Copestake and Briscoe,
1992), in which conventionalised and language specific aspects of
these general processes of conceptual transfer are expressed, and
which serve as language specific `filters' on the general process.

Polysemy as sense modulation through specialisation or broadening of
meaning in context is intuitively a common process.  Many examples
that lexicographers tend to treat as alternative senses are, in
principle, amenable to this approach; for instance, Atkins and Levin
(1992) identify two senses of {\it reel} appropriate to the
interpretation of {\it film reel} and {\it fishing reel} and
demonstrate that some but not all extant conventional dictionaries
list these two senses. Often the precise relationship between the
premodifier and the noun is treated as a question of pragmatics
(e.g.~Hobbs \etal., 1990; Alshawi, 1992:211).  However, if {\it reel} is
defined as a container artifact with the purpose of (un)winding, where
the material to be wound is left largely unspecified in the basic
entry, then this definition can be specialised with the appropriate
material by instantiation of the object of the (un)winding.  This
approach would be adequate to characterise the contribution of the
premodifier to the semantics of the phrase for the two examples above.
However, physical differences between types of reel would be treated
as outside the domain of lexical semantics. Pustejovsky (1991)
develops a theory of lexical semantics in which this approach to sense
modulation can be couched.  Under this account the representation of
nouns includes a specification of their {\em qualia structure}, which
encodes the form, content, agentive and telic (purpose) roles.  Thus
the telic role of the basic sense of {\it reel} would be partially
instantiated.  In general, Pustejovsky suggests that the notion of
semantic composition be enriched to one of `co-composition' in which
aspects of the nominal semantic representation are integrated with
aspects of the premodifier's semantics, using a combination of type
shifting of the predicate and type coercion of the nominal complement
(Pustejovsky, 1993). A related phenomenon is the broadening of a sense
in context; for example, {\it cloud} seems to have as a ``mass of
water vapour'' basic sense, but an extended usage as a mass of
anything floating {\it dust cloud}, {\it cloud of smoke}, or {\it
cloud of mosquitoes}.  One thing that normally characterises such
usages is the explicit contextual specification of the way in which
the sense has been broadened: thus we might treat the basic sense as
taking a default content qualia value which can be overridden by a
modifying phrase.

In what follows, we explore the hypothesis that systematic nominal
polysemies of the kind outlined above can be divided into two types of
process which we term constructional polysemy (sense modulation) and
semi-productive sense extension (sense change). In constructional
polysemy, the polysemy is more apparent than real, because lexically
there is only one sense and it is the process of syntagmatic
co-composition (Pustejovsky, 1991) which causes sense
modulation. Nevertheless, we argue that the range of possible
modification in co-composition is lexically specified, though
pragmatically defeasible. Many cases of pre- or post- nominal
modification, such as the examples of specialisation and broadening
above, as well as verbal logical metonymies can be analysed in this
fashion. Sense extension, on the other hand, requires lexical rules
which create derived senses from basic senses, often correlating with
morphological or syntactic changes.  Sense extension rules are semi-productive
and susceptible to processes such as blocking or preemption by
synonymy, and are, we argue, formally identical to other rules of
conversion and derivational morphology. Many cases of conventional
nominal metonymy, such as those introduced above, can be analysed in
these terms.

In \S2 we describe the lexical representation language that we have
developed to represent basic lexical entries and characterise
systematic lexical processes. In \S3 we return to constructional
polysemy and motivate a more detailed analysis of specialisation as
well as discussing broadening in this framework.  In \S4 we discuss
sense extension proper with respect to grinding, portioning and other
types of nominal metonymy; we address the issues of the directionality
of sense extensions, their apparent ability to apply to phrases in
some cases, and their productive yet highly conventionalised nature.
In \S5 we consider cases of `co-predication' (Pustejovsky, 1994),
where distinct senses are accessible for coordination and
modification, and present an analysis of some cases of co-predication
compatible with our accounts of constructional polysemy and sense
extension. In common with other lexical processes, sense extension is
semi-productive in that it is susceptible to blocking and sensitive to
frequency effects; in \S6 we argue that these properties can be
captured by adopting a probabilistic interpretation of lexical rules
and utilising probabilities in a natural fashion in language
production and interpretation.

\section{The Lexical Representation Language}

The language we will use to represent these classes of polysemous
behaviour is the lexical representation language (LRL) developed for
the ACQUILEX lexical knowledge base system (LKB).  The LRL is a typed
feature structure language (Carpenter, 1992), augmented with defaults
and lexical rules.  Types are used to structure lexical entries, which
are represented as feature structures (FS), and specify how they
combine by means of grammar rules, or alternatively, by constraints on
phrasal types.\footnote{LKB and LRL are thus something of a misnomer,
since the system is not specific to lexical representation, but is
also used for syntagmatic description.}  The LRL could be used to
implement a range of unification and constraint based approaches.  The
approach taken in this paper can be regarded (roughly) as combining an
HPSG-like approach to syntax with Pustejovsky's notion of qualia
structure.

Earlier versions of the LRL have been described in Copestake (1992,
1993a,b) and we will only provide a brief sketch of the formalism
here.  In this paper, however, we will make use of an improved notion
of default unification, which is order independent and allows for
persistent defaults (Lascarides \etal. (forthcoming), see \S\ref{pdu}
below).  Most previous definitions of default unification have assumed
that it involves incorporating into a non-default FS all the
consistent information from a default FS, making no distinction in the
result between information which arose from the default and
non-default structures.  In our treatment, by contrast, information in
FSs may be marked as default (or non-default), and this distinction
persists throughout subsequent default unification operations.
Another difference is an improved treatment of `lexical' rules, which
can now operate on both lexical and phrasal signs (see
\S\ref{lrules}).  Partially specified phrasal signs can also be
represented within the LRL.  In general terms, we are aiming at a
formalism which is adequate to represent the conventionalised,
non-fully productive aspects of the language, including words, idioms
and sense extension processes (which may be applicable to phrases as
well as words --- see \S4.3).  We will use {\it lexical} broadly to
include any such specification.\footnote{We assume that the lexicon
includes everything which is not completely compositional, that is not
regularly composed from the usual meanings that the components have in
isolation.}

\subsection{Types}
The LRL uses a definition of typing that largely follows
Carpenter (1992).  
The types are organised as a lattice, with top ($\top$) being the most
general type and bottom ($\bot$) indicating inconsistency.
This lattice, in effect, specifies
compatibility between types 
(any two types must have a unique 
greatest lower bound in the lattice --- they are compatible/unifiable if
this is not $\bot$) and also allows for inheritance
of constraints from types to subtypes (see
Figure~\ref{types}).   Constraints on types are themselves FSs, which will
subsume all well-formed FSs of that type --- the only features that may be
present on the node of a well formed FS are those appropriate to the type
labelling it (see Figures~\ref{typedesc} and~\ref{constraint}).
Furthermore, the type
hierarchy itself is interpreted as constraining the class of totally specified
or `ground' FSs, since it is assumed to be complete, with subtypes fully
covering their supertypes.  That is, given $t$ and $t'$ are subtypes of $t''$,
anything of type $t''$ must be resolved to be either $t$ or $t'$.  The process of
type resolution can be used to drive parsing and generation.
\setlength{\unitlength}{0.8in}
\begin{figure}
\begin{center}
\begin{picture}(6, 1.7)(-0.5, 1.4) 
\put(3,3.0){\makebox(0,0){\bf $\top$}}
\put(2.9,2.9){\line(-2, -1){0.6}}
\put(3.1,2.9){\line(2, -1){0.6}}
\put(3.0,2.9){\line(0, -1){0.3}}
\put(2.8,2.9){\line(-4, -1){0.7}}
\put(3.2,2.9){\line(4, -1){0.7}}
\put(3,2.5){\makebox(0,0){\bf string}}
\put(2,2.5){\makebox(0,0){\bf sign}}
\put(1.9,2.4){\line(-2, -1){0.6}}
\put(1,2.0){\makebox(0,0){\bf lex-sign}}
\put(0.9,1.9){\line(-2, -1){0.6}}
\put(0,1.5){\makebox(0,0){\bf lex-noun-sign}}
\put(4,2.5){\makebox(0,0){\bf nomqualia}}
\put(3.9,2.4){\line(-2, -1){0.6}}
\put(4.1,2.4){\line(2, -1){0.7}}
\put(5,2){\makebox(0,0){\bf artifact}}
\put(4.9,1.9){\line(-2, -1){0.6}}
\put(3,2){\makebox(0,0){\bf physical}}
\put(2.9,1.9){\line(-2, -1){0.6}}
\put(2,1.5){\makebox(0,0){\bf animal}}
\put(3,1.9){\line(0, -1){0.3}}
\put(3,1.5){\makebox(0,0){\bf plant}}
\put(3.1,1.9){\line(2, -1){0.6}}
\put(4,1.5){\makebox(0,0){\bf art\_phys}}
\end{picture}
\caption{A fragment of a type hierarchy}
\label{types}
\end{center}
\begin{minipage}[t]{72mm}
\begin{laureldesc}

{\bf top} ().\\[0.1in]
%
{\bf string} ({\bf top}).\\[0.1in]
%
{\bf sign} ({\bf top})\\
\> \verb+< ORTH > =+ {\bf string}.\\[0.1in]
%
{\bf lex-sign} ({\bf sign}).\\[0.1in]
%
{\bf lex-noun-sign} ({\bf lex-sign})\\
\> \verb+< QUALIA > =+ {\bf nomqualia}.\\[0.1in]
%
{\bf nomqualia} ({\bf top}).\\[0.1in]
%
{\bf physical} ({\bf nomqualia})\\
\> \verb+< FORM > =+ {\bf form}.\\[0.1in]
%
{\bf form} ({\bf top})\\
\> (OR {\bf mass} {\bf indiv} {\bf plural}).
\\[0.1in]
%
{\bf animal} ({\bf physical})\\
\> \verb+ < FORM > =+ {\bf indiv}\\
\> \verb+ < SEX > =+ {\bf gender}.
\end{laureldesc}
\end{minipage} 
\hfill
\begin{minipage}[t]{72mm}
\begin{laureldesc}
%
{\bf gender} ({\bf top})\\
\> (OR {\bf male} {\bf female}).\\[0.1in]
%
{\bf plant} ({\bf physical}).\\[0.1in]
%
{\bf artifact} ({\bf nomqualia})\\
\> \verb+< TELIC > =+ {\bf verb-sem}.\\[0.1in]
%
{\bf art\_phys} ({\bf physical} {\bf artifact}).\\[0.2in]
%
{\bf verb-sem} ({\bf top})\\
\> \verb+< IND > =+ {\bf eve}\\
\> \verb+< PRED > =+ {\bf string}\\
\> \verb+< ARG1 > = < IND >+\\
\> \verb+< ARG2 > =+ {\bf obj}\\
\> \verb+< ARG3 > =+ {\bf obj}.\\[0.1in]
%
{\bf sem} ({\bf top}).\\[0.1in]
% 
{\bf eve} ({\bf sem}).\\[0.1in]
%
{\bf obj} ({\bf sem}).
\end{laureldesc}
\end{minipage}
\caption{Description of illustrative type system}
\label{typedesc}

\vspace*{1mm}

{\centering
\tiny
   $\avmplus{\att{art\_phys}\\
             \attvaltyp{FORM}{form}\\
             \attval{TELIC}{\avmplus{\att{verb-sem}\\
                                  \attval{IND}{\ind{0}}\ \ \myvaluebold{eve}\\
                                  \attvaltyp{PRED}{string}\\
                                  \attval{ARG1}{\ind{0}}\\
                                  \attvaltyp{ARG2}{obj}\\
                                  \attvaltyp{ARG3}{obj}}}}$

}
\caption{Expanded constraint on {\bf art\_phys}}
\label{constraint}
\end{figure}

\subsection{Lexical descriptions}
\label{pdu}

In the LKB, the type language is
augmented with a lexical description language that incorporates
lexical rules and default inheritance.   
Lexical entries are defined in terms of types, for example:
\begin{laureldesc}
book 1\\
\> \verb+< > =+ {\bf lex-noun-sign}\\
\> \verb+< QUALIA > =+ {\bf art\_phys}\\
\> \verb+< QUALIA TELIC PRED > =+ {\bf read}\\
\> \verb+< QUALIA FORM > =+ {\bf indiv}.
\end{laureldesc}
(Here we continue to use the simple type system defined in Figure~\ref{typedesc}.)
The 
FS is defined to have overall type {\bf lex-noun-sign} and to have
the {\feature qualia} appropriate for an individuated physical artifact
with a telic role instantiated to {\it read}.
The {\feature orth} feature is instantiated with a string constructed
from the entry's label, {\bf {\tt "}book{\tt "}}
(string types do not have to be explicitly listed in the system).

Lexical descriptions are
evaluated to produce {\it psort}s, which are simply named FSs.  
We make use of psorts rather than define distinct
types for each lexical entry mainly because we have found
the restrictions on the type system to be inappropriate for lexical
entries --- we discuss this in more detail below.
Various inheritance
relationships are defined to operate on psorts.
In theory, arbitrary parts of FSs can be related by inheritance.  In
practise, we make use of two classes of inheritance specification much more
extensively than others.  One of these is inheritance of qualia structure,
the other is used in describing a lexical entry as being
derived via a productive rule, but having some exceptional value for
orthography, syntax or semantics.  We will concentrate on qualia
inheritance here since it is more relevant to the subsequent discussion,
but see Copestake (1992) for a treatment of lexical exceptions in the LKB.

We assume that the possible qualia structures can be regarded as a
conceptual hierarchy (actually a lattice), certain regions of which will
be associated with particular lexical entries.  
It is convenient to be able
to describe some lexical entries as inheriting their qualia structure from
others (see Copestake, 1992, 1993a).  For example:  
\begin{laureldesc}
novel 1\\
\> \verb+< QUALIA >   <  book_1 < QUALIA >+. 
\end{laureldesc}
states that the lexical entry for a particular sense of
{\it novel} inherits its qualia from (a particular sense of) {\it book}. 
(The symbol {\tt <} indicates inheritance.)  Given this
specification, {\it novel} would inherit its telic role from {\it book}.
One effect of this is that it
would predict that the normal interpretations of \exnum{+1}{a} and 
\exnum{+1}{b} below would both involve a reading event (see Pustejovsky,
1991 and \S\ref{fast}, below).
\begin{ex}
\begin{subex}
John enjoyed the book.
\end{subex}
\begin{subex}
John enjoyed the novel.
\end{subex}
\end{ex}

However, 
inheritance of individual qualia must be defeasible.  For example,
{\it dictionary} should also be defined to inherit its qualia structure from  
{\it book} but has a telic role of {\bf refer\_to} rather than
{\bf read}.   
Default inheritance in the LKB is now formalised in terms of persistent default
unification (PDU).  We will give only a brief description of this here:
it is fully defined in
Lascarides \etal. (forthcoming).   
This treatment of typed
default unification is an improvement over that used previously in the LKB
(Copestake, 1992,1993a) in that it is order independent and allows for
persistent defaults.  This allows us to define multiple orthogonal 
default inheritance in the lexicon in a manner
which is fully declarative.
Furthermore, the earlier definition of default inheritance in terms of a
default unification operation applying to normal FSs,
was restricted in applicability to lexical descriptions, but
defaults may now persist outside the lexicon.  Thus defaults may be
combined during the interpretation/generation of a sentence and 
defaults which originate from lexical specifications can interact with
pragmatic processing.
In our new definition, parts of FSs may be defeasible; this is a necessary condition
for default unification to be associative.  In this respect, PDU is similar
to the notion of defaults in Young and Rounds (1993), but their approach is limited
in that their definition is restricted to non-reentrant values and in that they
assume an untyped framework.  In contrast, PDU uses the type hierarchy to
prioritise defaults.  

We use a slashed notation for partially defeasible FSs
where values to the left of the slash are indefeasible and those to the
right defeasible ({\it indefeasible/defeasible}).
We abbreviate this to {\it /defeasible} where the indefeasible value is
uninteresting (e.g. where it is $\top$) and omit the slash when there is no
(interesting) defeasible value.
So, for example, the FS for {\it book}, shown in
Figure~\ref{book}, specifies that the value for the telic predicate is
defeasible.
\begin{figure}
{\centering
\tiny
   $\avmplus{\att{lex-noun-sign}\\
             \attvaltyp{ORTH}{book}\\
             \attval{QUALIA}{\avmplus{\att{art\_phys}\\
                                       \attvaltyp{FORM}{indiv}\\
                                 \attval{TELIC}{\avmplus{\att{verb-sem}\\
                                  \attval{IND}{\ind{0}}\ \ \myvaluebold{eve}\\
                                  \attvaltyp{PRED}{/read}\\
                                  \attval{ARG1}{\ind{0}}\\
                                  \attvaltyp{ARG2}{obj}\\
                                  \attvaltyp{ARG3}{obj}}}}}}$

}
\caption{FS for {\it book}}
\label{book}
\end{figure} 
The description given below for {\it dictionary} specifies that it 
inherits its qualia structure from {\it book}
but the specific default
value {\bf refer\_to} overrides the inherited value of the telic
predicate.   
\begin{laureldesc}
dictionary 1\\          
\> \verb+< QUALIA > < book_1 < QUALIA >+\\
\> \verb+< QUALIA TELIC PRED > = /+{\bf refer\_to}.
\end{laureldesc} 
We specify the value of the telic predicate to be defeasible here as well,
because for some dictionaries this might not be appropriate (e.g. 
Bierce's Devil's Dictionary) and also because the contribution of the telic
role to interpretation of a particular sentence is potentially defeasible.
The corresponding FS is shown in Figure~\ref{dictionary}.\footnote{We have
assumed here for ease of exposition
that the constraint specifications in the type system are all
non-defeasible, although this will not be true in general.  Type
resolution, however, is determined by the indefeasible constraints and
there is no notion of a `default link' in the type hierarchy itself, so the
formalisation of the type system itself remains very similar.}
\begin{figure}
{\centering
\tiny
   $\avmplus{\att{lex-noun-sign}\\
             \attvaltyp{ORTH}{dictionary}\\
             \attval{QUALIA}{\avmplus{\att{art\_phys}\\
                                       \attvaltyp{FORM}{indiv}\\
                                 \attval{TELIC}{\avmplus{\att{verb-sem}\\
                                  \attval{IND}{\ind{0}}\ \ \myvaluebold{eve}\\
                                  \attvaltyp{PRED}{/refer\_to}\\
                                  \attval{ARG1}{\ind{0}}\\
                                  \attvaltyp{ARG2}{obj}\\
                                  \attvaltyp{ARG3}{obj}}}}}}$

}
\caption{FS for {\it dictionary}}
\label{dictionary}
\end{figure} 

One effect of the difference in telic role between {\it book} and {\it
dictionary} is due to the different aspectual properties of the predicates;
{\bf read} can describe a process but {\bf refer\_to} is point-like.
Since
{\it enjoy} selects for a process, \exnum{+1}{} is odd.
\begin{ex}
? John enjoyed the dictionary.
\end{ex}
The importance of the defeasibility of parts of the qualia structure
is discussed briefly in \S\ref{fast} and at more length in Lascarides
\etal. (forthcoming).  The persistence of the defaults `outside' the
lexicon is irrelevant for much of this paper, so for the most part we
can continue to assume the formal account of the LKB provided by
Copestake (1992; 1993b) and we, therefore, omit further discussion of
PDU.

There are a number of reasons for not defining lexical entries to be
types themselves.  We want to maintain a distinction between the
types, which are used for description or classification, and the data
which they are being used to classify --- i.e.~the lexical entries.
The type system is assumed to be complete, but we do not want to make
this assumption about hierarchically arranged lexical entries.  It
should not be necessary or even possible to introduce features which
are specific to particular lexical entries.  The hierarchical
organisation of the psorts is used for inheritance of information, but not for
classification of words.  
Furthermore the condition imposed on the type
hierarchy, that a unique greatest lower bound must be explicitly
specified for all compatible types, is too restrictive to apply to the
lexical entries, or parts of lexical entries, that we refer to as
psorts.  The FSs, of course, do form a lattice, but the points that
are being specifically identified as psorts do not.  Psorts are a way
of identifying particular points in the lattice, but which points are
so identified is not constrained in any way.

Furthermore, making lexical entries types obviously leads to a
proliferation of types.  This is particularly acute if we wish to make some
lexical entries underspecified with respect to the lexical types.  For
example, suppose we wished to make {\it truth} underspecified with respect to
the two types {\bf lex-count-noun} and {\bf lex-uncount-noun} which were both
defined as subtypes of {\bf lex-noun}.   Simply specifying {\bf truth} as
an additional
subtype of {\bf lex-noun} would not achieve the correct results, since it
would then not unify with a FS of type {\bf lex-count-noun} or {\bf
lex-uncount-noun}.  We would have to explicitly define {\bf truth-count} as a
subtype of {\bf truth} and {\bf lex-count-noun} and similarly for {\bf
truth-mass} (which means there would be no advantage of economy of
representation in the underspecification). 
\footnote{In any event, there would be severe practical problems in
constructing such a system, given that the type system would have to
be recompiled each time a lexical entry was added.}  Instead we define
lexical entries as FSs, but give them a special status in that they
are identifiable and constrain the results of evaluating FSs which
have lexical types.

In the current version of the LRL, we define psorts as constraints on certain
types.  If a type is defined as being {\it lexical} 
it is assumed to be constrained such that any FS
to which it is resolved must be subsumed by one or more psorts of the
appropriate type.  
For example, Figure~\ref{extype} shows a FS 
and the possible resolutions, given the psorts shown and the types in
Figure~\ref{types}. 
If a type is defined as being {\it phrasal} it will normally be 
resolved as being constructed
from lexical types, which will be constrained by lexical psorts.
However it is also
possible for phrasal psorts to be defined which allow an alternative
analysis of the phrase. 
These will not be fully resolved FSs, but partially specified ones which
will themselves be subject to constraint resolution.  
(This mechanism might also used in the treatment
of idioms and other (partially) fixed phrases.)
\begin{figure}
\begin{laureldesc}
%
rabbit\\
\> \verb+<> =+ {\bf lex-noun-sign}\\
\> \verb+< QUALIA > =+ {\bf animal}.\\[0.1in]
%
bull\\
\> \verb+<> =+ {\bf lex-noun-sign}\\
\> \verb+< SEX > =+ {\bf male}.
\end{laureldesc}
Query FS:
{\tiny
   $\avmplus{\att{lex-sign}\\
             \attvaltyp{ORTH}{string}\\
             \attval{QUALIA}{\avmplus{\att{nomqualia}\\
                                       \attvaltyp{SEX}{male}}}}$}\\
Resolved FSs:
{\tiny
   $\avmplus{\att{lex-noun-sign}\\
             \attvaltyp{ORTH}{rabbit}\\
             \attval{QUALIA}{\avmplus{\att{animal}\\
                                       \attvaltyp{FORM}{indiv}\\
                                       \attvaltyp{SEX}{male}}}}$},
{\tiny
   $\avmplus{\att{lex-noun-sign}\\
             \attvaltyp{ORTH}{bull}\\
             \attval{QUALIA}{\avmplus{\att{animal}\\
                                       \attvaltyp{FORM}{indiv}\\
                                       \attvaltyp{SEX}{male}}}}$}
\caption{Constraint resolution with lexical constraints}
\label{extype}
\end{figure}

\subsection{Lexical rules}
\label{lrules}

Lexical rules are formalised in the LKB as
feature structures of type {\bf lexical-rule}, which
has the constraint:
\begin{center}
{\tiny
   $\avmplus{\att{lexical-rule}\\
             \attvaltyp{0}{lex\_sign}\\
             \attvaltyp{1}{lex\_sign}}$} 
\end{center}
Application of a particular lexical rule simply involved unification of
the input of the psort with the input part of the lexical rule,
indicated by the path \verb|<1>|,
and returns the instantiated output of the rule, given by the path
\verb|<0>|.

An example of a lexical rule in this system is {\psort portioning},
which covers the sense extension involved in usages such as {\it three
beers}, where a mass noun which denotes some food or drink is converted to
a count noun denoting some (conventionally served) portion of that substance.
The FS in Figure~\ref{portioning} describes this rule
using the type system from Copestake (1992)
(the justification for the particular details of the representation adopted
can be found there).
The qualia types {\bf c\_obj} and {\bf c\_subst} indicate an edible
object and substance respectively.
The rule would apply to a lexical entry such as that shown for {\it beer}
in Figure~\ref{beer}.
Morphological rules are formally identical to sense extension rules, except in
specifying a change of phonology/orthography.
\begin{figure}
{\centering
\tiny
$\avmplus{\att{lexical-rule}\\
         \attval{0}{\avmplus{\att{lex-count-noun}\\
                  \attval{ORTH}{\ind{0}}\ \ \myvaluebold{orth}\\
                  \attvalshrunktyp{CAT}{noun-cat}\\
                  \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                           \attval{IND}{\ind{1}}\ \ \boxvaluebold{obj}\\
                           \attval{PRED}{\avmplus{\att{modified-pred}\\
                                                \attvaltyp{MODIFIER}{portion}\\
                                                \attval{MODIFIED}{\ind{2}}\ \ \myvaluebold{logical-pred}}}\\
                           \attval{ARG1}{\ind{1}}\\
                           \attvaltyp{PLMOD}{boolean}\\
                           \attvaltyp{QUANT}{boolean}}}\\
                  \attval{QUALIA}{\avmplus{\att{c\_obj}\\
                           \attval{TELIC}{\ind{4}}\ \ \boxvaluebold{verb-sem}\\
                           \attval{FORM}{\avmplus{\att{nomform}\\
                                    \attvaltyp{RELATIVE}{portion}}}\\
                           \attval{OBJECT-INDEX}{\ind{1}}}}}}\\
         \attval{1}{\avmplus{\att{lex-uncount-noun}\\
                  \attval{ORTH}{\ind{0}}\\
                  \attvalshrunktyp{CAT}{noun-cat}\\
                  \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                           \attval{IND}{\ind{5}}\ \ \boxvaluebold{obj}\\
                           \attval{PRED}{\ind{2}}\\
                           \attval{ARG1}{\ind{5}}\\
                           \attvaltyp{PLMOD}{boolean}\\
                           \attvaltyp{QUANT}{false}}}\\
                  \attval{QUALIA}{\avmplus{\att{c\_subst}\\
                           \attval{TELIC}{\ind{4}}\\
                           \attval{FORM}{\avmplus{\att{nomform}\\
                                    \attvaltyp{RELATIVE}{mass}}}\\
                           \attval{OBJECT-INDEX}{\ind{5}}}}}}}$

}
\caption{Lexical rule for portioning. 
In this figure, and subsequent examples, boxes round
type labels for a node (e.g. {\bf noun-cat})
indicate that the FS which that node heads is not
shown and some features are omitted.}
\label{portioning}
\end{figure}
\begin{figure}
{\centering
\tiny
$\avmplus{\att{lex-uncount-noun}\\
                  \attval{ORTH}{beer}\\
                  \attvalshrunktyp{CAT}{noun-cat}\\
                  \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                           \attval{IND}{\ind{1}}\ \ \boxvaluebold{obj}\\
                           \attval{PRED}{beer\_1}\\
                           \attval{ARG1}{\ind{1}}\\
                           \attvaltyp{PLMOD}{false}\\
                           \attvaltyp{QUANT}{false}}}\\
                  \attval{QUALIA}{\avmplus{\att{c\_subst}\\
                           \attvalshrunktyp{TELIC}{verb-sem}\\
                           \attval{FORM}{\avmplus{\att{nomform}\\
                                    \attvaltyp{RELATIVE}{mass}}}\\
                           \attval{OBJECT-INDEX}{\ind{1}}}}}$

}
\caption{FS corresponding to the lexical entry {\it beer}}
\label{beer}
\end{figure}

One immediate question is how the notion of lexical rules fits into a
constraint based framework.  In Copestake and Briscoe (1992), lexical
rules were essentially indistinguishable from grammar rules, and could
in fact apply to phrases.  This allowed us to deal with some examples
of phrasal sense extension. For example, the {\tt place -> group} sense
extension applies both to place denoting words such as {\it village}
and to some phrases, as in \exnum{+1}{} (see \S4.3 below, for further
details).
\begin{ex}
The south side of Cambridge voted Conservative.
\end{ex}
But treating lexical rules as operating as unary grammar rules is
unattractive --- it
obscures the distinction between the syntagmatic component of the system and the
semi-productive paradigmatic component.  
Furthermore this treatment does not carry over in a simple way to a
constraint based approach.  Within a strictly constraint based framework 
there have been essentially three proposals for lexical rules:
\begin{enumerate}
\item Lexical rules expand the lexicon in a preliminary processing phase.
This is the standard approach (e.g. Pollard and Sag, 1987) but is
unattractive because it does not extend to analogous phrasal
processes and because the lexicon is not finite.  
\item  Treat lexical rules as being similar to grammar rules, with affixes
having their own lexical entries.  Such an approach is suggested in Krieger
and Nerbonne (1993) for derivational morphology.  But for sense extension
and conversion we would need to postulate zero-morphemes.
\item The place of lexical rules is taken by complex types (Riehemann
1993).  For example, Figure~\ref{rportioning}, sketches a complex type which
could replace the portioning rule shown before.  
This avoids the use of zero-morphemes for
sense extension.  However, it still has disadvantages --- there is a
proliferation of types in the hierarchy as it becomes necessary to allow
lexical signs of all classes which might be formed by 
sense extension to be either simple or of a type that depends on their
derivation.
For example, {\bf lex-count-noun} would have subtypes {\bf
simple-lex-count-noun} and {\bf portioned}.  
Signs would be distinguished in this way solely because of their
construction from lexical rules, which is particularly 
unintuitive for sense extensions since the directionality of an extension
may be non-obvious (see \S4.5 below).
Extending the
approach to phrasal signs would be possible, but would further increase the
number of types. 
Thus this approach would work for our purposes, but the mechanics of
constraint resolution are driving the representation, forcing us to
postulate unnecessarily complex structures.  
\end{enumerate}
\begin{figure}
{\centering
\tiny
$\avmplus{\att{portioned}\\
       \attval{MORPH}{\avmplus{\att{complex}\\
               \attval{ORTH}{\ind{0}}\\
               \attval{DTR}{\avmplus{\att{lex-uncount-noun}\\
                           \attval{MORPH}{\avmplus{\att{morph}\\
                                           \attval{ORTH}{\ind{0}}}}\\
                           \attvalshrunktyp{CAT}{noun-cat}\\
                           \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                               \attval{IND}{\ind{3}}\ \ \boxvaluebold{obj}\\
                               \attval{PRED}{\ind{2}}\\
                               \attval{ARG1}{\ind{3}}}}}}}}\\
         \attvalshrunktyp{CAT}{noun-cat}\\
         \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                    \attval{IND}{\ind{1}}\ \ \boxvaluebold{obj}\\
                    \attval{PRED}{\avmplus{\att{modified-pred}\\
                        \attvaltyp{MODIFIER}{portion}\\
                        \attval{MODIFIED}{\ind{2}}\ \ \myvaluebold{logical-pred}}}\\
                    \attval{ARG1}{\ind{1}}}}}$

}
\caption{Portioning expressed as a complex type}
\label{rportioning}
\end{figure}

We treat lexical rules as generating psorts.  Clearly, if we simply
applied all the lexical rules to the defined psorts in a
precompilation phase, this would be equivalent to the first option
above.  Instead of doing this, we use the lexical rules to dynamically
generate alternatives during constraint resolution of nodes with
lexical types.  To see how this works, consider the example type
system in Figure~1, but assume that instead of the type {\bf animal}
we have a type {\bf animate}, with subtypes {\bf animal} and {\bf
human}.  Figure~\ref{lrex} shows a very simple lexicon and a lexical rule
that converts {\bf animal} denoting nouns to {\bf human} denoting
ones.\footnote{We are using this as a simple example purely to
explain the lexical rule mechanism, but we would, in fact, propose an
animal{\tt->}human rule to allow for (some aspects of) the
metaphorical uses of {\it pig}, {\it worm}, {\it rabbit} and so on.}
The query structure shown in Figure~\ref{lrex} might be resolved by
the lexical psort given for {\it grandmother}.  However an alternative
resolution is available via application of the lexical rule.
Figure~\ref{lrex} shows how this is applied in effect, by `wrapping'
it round the query FS which instantiates the output sign of the rule
and constraint resolving the result.  Further resolution of the input
sign, because it is matched up with a psort in the lexicon, results in
specialisation of values on the output sign (the {\feature orth} value
in this case).  The index $\ind{EX}$ is shown here to emphasise that
under normal circumstances this resolution step would be part of the
resolution of a sentence sign and thus the query FS shown will be part
of a larger structure.  Further constraints imposed on the output sign
by the resolution of the surrounding structure would affect the input
sign and thus limit the way in which it might be resolved.  Note that
this treatment implies that the output sign be resolvable with respect
to the type system: it must be a potential lexical psort even though
it is not actually defined as such.
\begin{figure}
\begin{laureldesc}
%
rabbit\\
\> \verb+<> =+ {\bf lex-noun-sign}\\
\> \verb+< QUALIA > =+ {\bf animal}.\\[0.1in]
%
grandmother\\
\> \verb+<> =+ {\bf lex-noun-sign}\\
\> \verb+< QUALIA > =+ {\bf human}\\
\> \verb+< SEX > =+ {\bf female}.\\[0.1in]
%
animal-metaphor\\
\> \verb+<> =+ {\bf lexical-rule}\\
\> \verb+< 0 ORTH > = < 1 ORTH >+\\
\> \verb+< 0 QUALIA > =+ {\bf human}\\
\> \verb+< 1 QUALIA > =+ {\bf animal}\\
\> \verb+< 1 QUALIA SEX > = < 0 QUALIA SEX >+.
\end{laureldesc}
\begin{tabular}{ll}
Query FS: &
{\tiny
   $\ind{EX} \ \
         \avmplus{\att{lex-noun-sign}\\
             \attvaltyp{ORTH}{string}\\
             \attval{QUALIA}{\avmplus{\att{human}\\
                                       \attvaltyp{SEX}{female}}}}$}\\
Lexical rule applied: &
{\tiny
   $\avmplus{\att{lexical-rule}\\
             \attval{0}{\ind{EX}} \ \ \avmplus{\att{lex-noun-sign}\\
             \attval{ORTH}{\ind{0}}\\
             \attval{QUALIA}{\avmplus{\att{human}\\
                                       \attval{SEX}{\ind{1}} \ \ \myvaluebold{female}}}}\\
             \attval{1}{\avmplus{\att{lex-noun-sign}\\
             \attval{ORTH}{\ind{0}}\\
             \attval{QUALIA}{\avmplus{\att{animal}\\
                                       \attval{SEX}{\ind{1}}}}}}}$}\\
Resolved FSs: &
{\tiny
   $\avmplus{\att{lexical-rule}\\
             \attval{0}{\ind{EX}} \ \ \avmplus{\att{lex-noun-sign}\\
             \attval{ORTH}{\ind{0}}\ \ \myvaluebold{rabbit}\\
             \attval{QUALIA}{\avmplus{\att{human}\\
                                       \attvaltyp{FORM}{indiv}\\
                                       \attval{SEX}{\ind{1}} \ \ \myvaluebold{female}}}}\\
             \attval{1}{\avmplus{\att{lex-noun-sign}\\
             \attval{ORTH}{\ind{0}}\\
             \attval{QUALIA}{\avmplus{\att{animal}\\
                                       \attvaltyp{FORM}{indiv}\\
                                       \attval{SEX}{\ind{1}}}}}}}$}
\end{tabular}
\caption{Constraint resolution with lexical rules}
\label{lrex}
\end{figure}

This stategy involves a slight modification to the constraint resolution
algorithm since it entails an external mechanism adding a node to be resolved.  
Resolution of this node could itself involve
lexical rule application, of course, and in general, this algorithm may not
terminate.  This, however, also applies to the alternative formalisations.
Compared with Riehemann's approach, we are trading off greater simplicity in
the type system with a complication of the constraint resolution 
mechanism. From our viewpoint, one advantage is
that we are maintaining a distinction between the
straightforwardly syntagmatic aspects of the grammar, which are
implemented by means of phrasal types, and the semi-productive
processes we implement by lexical rules.

Our approach straightforwardly applies to phrases, such as
example \exnum{0}{} above where {\it south side of Cambridge} denotes the group of
people living there. 
In these cases the input form (e.g. {\it south side of Cambridge} denoting
the place) will be a
phrase with daughters
({\feature DTRS}) which will themselves be further resolved in the
usual way.
The output structure must also be resolvable with respect to the type
system.
The phrasal sense extensions we have encountered so far all apply to signs
which could be either lexical or phrasal as far as the context of the rest
of the sentence is concerned (i.e.~lexical items could be
substituted for them without affecting grammaticality).  Since
multiword orthography does not necessitate the possession of a
{\feature DTRS} attribute, the lexical rule can be defined so that the
output form is treated as
a lexical type and will not have daughters to be resolved.  

\section{Constructional Polysemy}
\label{fast}

There are many cases of apparent polysemy which we would argue are
better treated as `constructional' polysemy, in that the lexical item
is assigned one (often more abstract) sense and processes of
syntagmatic combination or `co-composition' (Pustejovsky, 1991) are
utilised to specialise this sense appropriately.   
We treat this as a process of sense modulation, represented by
specialisation in the LKB, in contrast to the process of sense extension to
be discussed in the next section, which we represent using lexical rules.

A simple example of specialisation is the representation of {\it reel}
in its container sense.  It is reasonable to define a type {\bf
container} shown in Figure~\ref{container} that has both syntactic and
semantic effects, since container nouns as a class can be
subcategorised for postmodification with an {\it of} phrase denoting
their contents (e.g.~{\it reel of tape}) which then can be regarded as
instantiating their constitutive role.  Thus, the polysemy involved in
the distinction between e.g.~ {\it film reel} and {\it fishing reel}
is not regarded as lexical, and the entry for {\it reel} is simply:
\begin{laureldesc}
reel 1\\
\verb+<> =+ {\bf container}.
\end{laureldesc}
The constitutative role may be instantiated by syntagmatic combination
(e.g.~{\it reel of film}) but in some cases it may only be implicit in the
context. 
\begin{figure}
\begin{picture}(6, 3)(0, 3)
\put(3,5){\makebox(0,0){\bf lex-count-noun}}
\put(3.1,5.1){\line(2,1){0.6}}
\put(2.9,4.9){\line(-2,-1){0.6}}
\put(2,4.5){\makebox(0,0){\bf container}}
\put(2,4.4){\makebox(0,0)[t]{\tiny $\avmplus{\attvaltyp{QUALIA}{art\_phys}}$}}
\put(1.9,4.2){\line(-2,-1){0.6}}
\put(1,3.8){\makebox(0,0){\bf container0}}
\put(2.1,4.2){\line(2,-1){0.6}}
\put(3,3.8){\makebox(0,0){\bf container-of}}
\put(4.2,3.6){\makebox(0,0)[t]
{\tiny $\avmplus{\attvallist{CAT SUBCAT}{\avmplus{\attval{SEM}{\ind{0}}\\
                                           \attval{QUALIA TELIC}{\ind{1}}}}\\
                 \attval{QUALIA}{\avmplus{\attval{CONSTITUENCY}{\ind{0}}\\
                                         \attval{TELIC}{\ind{1}}}}}$}}
\put(3.9,4.2){\line(-2,-1){0.6}}
\put(4,4.5){\makebox(0,0){\bf rel\_noun}}
\put(4,4.4){\makebox(0,0)[t]{\tiny $\avmplus{\attvaltlist{CAT SUBCAT}{PP}}$}}
\put(4.9,4.9){\line(-2,-1){0.6}}
\end{picture}
\caption{Outline of the description of container nouns}
\label{container}
\end{figure}


There is, however, another source of polysemy, since container nouns as a
class can also refer to their contents.  Thus in a \exnum{+1}{}
{\it reel} can be used to refer to the film it contains.
\begin{ex}
I just accidentally exposed three reels [ of Ektachrome ].
\end{ex}
Furthermore, some types of polysemy will apply only to some subpart of the
sense described by the lexical entry.  In this particular case, {\it reel}
used of cinema films can have an abstract sense denoting part of the film:
\begin{ex}
The mystery is only resolved in the final reel.
\end{ex}
Here we have a sense extension from a physical object used for
representation (in this case the contained object) to the abstract
entity represented.  Other examples of this extension will be discussed in more
detail in \S\ref{newspaper}.  The point here is that it is the
instantiated form of the basic entry which determines what senses are
available, emphasising the need for flexible interaction between
syntagmatic combination and lexical rules.

A more complex example of specialisation by constructional polysemy is
adjectival premodification; it is well known that in examples such as
\exnum{+1}{}, the adjectives take on different meanings depending on
the nature of the modified head.
\begin{ex}
\begin{subex}
a sad poem / poet / day
\end{subex}
%\begin{subex}
%a noisy person / party
%\end{subex}
\begin{subex}
a fast motorway / car / driver
\end{subex}
\end{ex}
Such examples have been used to argue that adjectives should be
treated as higher-order predicates or should introduce an unspecified
predicate representing the relation between the property denoted by
the adjective and that denoted by the head noun (e.g.~Hobbs \etal., 1990).
Pustejovsky (1991; 1993) argues that some such adjectives can be
analysed as predicates which coerce the type of the head and operate
on its qualia structure. Thus he analyses {\it fast} as a predicate
which selects the eventive qualia accessible through the entries for
the head nouns in \exnum{0}{b}.\footnote{Briscoe \etal. (1990) and
Godard and Jayez (1993) point out that there are problems with
Pustejovsky's technical approach to type coercion relating to
co-predication (see \S5 and below). We omit details of this proposal
here, which is described most fully in Pustejovsky (1993).} The
claim is that nouns denoting artifacts make available as part of their
lexical specification an agentive and telic role representing their
(typical) process of creation and of use, respectively. Similarly
deverbal nouns make their underlying verbal predicate accessible in
the same manner.  Thus, an adjective selecting an eventive argument
`coerces' the type of the noun into one of the eventive qualia or the
predicate underlying the deverbal noun.

Pustejovsky (1991, 1993) also discusses other examples of `logical
metonymy', in which the semantics of a verbal predicate and the type
of its complement exhibit mismatches, such as \exnum{+1}{}.
\begin{ex}
\begin{subex}
Sam enjoyed (drinking) the beer
\end{subex}
\begin{subex}
Sam enjoyed (watching) the film
\end{subex}
\begin{subex}
Sam enjoyed (reading) the book
\end{subex}
\begin{subex}
Sam enjoyed (eating) the caviar
\end{subex}
\end{ex}
{\it enjoy} subcategorises for a NP or progressive VP complement
syntactically, but semantically requires a complement with an eventive
interpretation in which the experiencer subject of {\it enjoy}
participates as understood subject. Each of the examples in
\exnum{0}{} is grammatical with or without the bracketed progressive
participle. However, in the case where it is not present the
interpretation remains (by default) identical. Analogously, to the
case of adjectival modification, Pustejovsky (1993) captures the
similarity between the two subcategorisation possibilities for {\it
enjoy} by means of a type shifting operator applied to the predicate,
and uses a type coercion operator which selects from the eventive
qualia of the NP artifact-denoting complement to express the
`co-compositional' aspect of the resultant interpretation.

Briscoe \etal. (1990) presents an analysis of logical metonymies with
{\it enjoy} which is based on treating type coercion as a (unary)
grammatical rule which alters the type and interpretation of the NP.
However, Copestake and Briscoe (1992) and Godard and Jayez (1993)
point out problems with this analysis stemming from possibilities of
`co-predication'; for example, it seems quite possible to coordinate
predicates which require physical objects and events as complements,
as in
\exnum{+1}{}.
\begin{ex}
\begin{subex}
Sam picked up and finished his beer
\end{subex}
\begin{subex}
Sam ate and enjoyed the caviar
\end{subex}
\begin{subex}
Sam wrote but later regretted that article
\end{subex}
\end{ex}
Therefore, we treat this type of polysemy as a question of selecting
the appropriate aspect of the meaning of the complement, rather than a
change in the meaning of the NP itself. Traditionally, this is closest to
saying that nouns denoting artifacts are vague, rather than ambiguous,
between eventive and objective readings, in these contexts.

Consider first the example of {\it fast typist}.  The effect we want is for 
{\it fast} to apply to events of the typist typing --- i.e.~the paraphrase
of {\it fast typist} is (by default) {\it typist who types fast}.  We will
assume that we do this by reifying the event, giving a logical form
equivalent to:\footnote{We use a linearised form equivalent 
to the FS representation 
here for readability.  We will leave some aspects of the representation
incomplete where the details are not relevant to our main concerns.
For example, we do not specify here 
how the event variable $e$ should be bound.  Simple existential quantification
looks unsatisfactory since there seems to be something
generic or habitual about {\it fast typist}. One possible
approach might be to treat the domain of events as having a
lattice structure (e.g. Krifka, 1987) which would allow us to make the
event referred to as {\it fast} 
the composite of subevents of the typist typing 
(cf Ojeda, 1993, on generic nominals) or perhaps the composite of some contextually
salient subevents.  Since {\it fast} need not be fully distributive, this
would not imply that all subevents were {\it fast}.
But we have not worked out the details of such a treatment since
it is not at all obvious how many typing events {\it fast} ought to apply to.
Most work on generics and habituals makes the assumption that they can be
paraphrased using {\it normally} or {\it usually}, but it is 
not clear that this is true of {\it fast typist}, {\it fast car} etc.
It is possible to assert that Bill is a {\it fast typist} even if he
usually types at 20 words per minute but was observed doing 120 wpm
in a competition.  An individual car can perhaps be truthfully
said to be fast even if it has
never been driven above 40mph yet, as long as its potential is known.  
This situation is not peculiar to this class of
adjectival modification: {\it John eats snails}, for example, can be true
even if he has only done so once or twice (cf Pelletier and Schubert's (1988)
comments on {\it Frenchmen eat horsemeat} and similar examples).}
\[ [ x ] [ typist (x) \wedge fast (e) \wedge type (e, x)] \]

We achieve this result by assuming that the qualia
structure for {\it typist} has its telic role instantiated to:
\[ [ x ] [ type (e, x) ] \]
where $x$ is coindexed with the `normal' variable.\footnote{The 
status of qualia structure
in our approach is slightly different to that of 
Pustejovsky and Boguraev (1993) in that we include qualia structure in the {\it
lexical} representation of the noun (as a component of a FS in the
LKB) and specify type coercion in unification based terms.
However, we also recognise the need for interaction between qualia
structure derived stereotypical eventive readings and other
pragmatically or contextually determined interpretations. In our
account, the stereotypical reading is specified by default as a
by-product of the parsing process, but can be overridden pragmatically
(see Briscoe \etal., 1990; Lascarides \etal., forthcoming).}
Thus the lexical entry for {\it typist} contains structures equivalent to
the following:
\begin{quote} 
$\langle\mbox{\rm SEM}\rangle [ x ] [ \mbox{\rm typist} (x) ]$\\
$\langle\mbox{\rm QUALIA TELIC}\rangle [ x ] [ \mbox{\rm type} (e, x) ]$
\end{quote}
The type {\bf adjective} has subtypes for
adjectives that select the telic role, the agentive role and so on.
The basic type 
{\bf adjective} is subcategorised for nouns, and has the following
semantics:
\[ [ x ] [ \mbox{\rm adj-pred} (w) \wedge P (w, x) ] \]
The treatment is similar to that proposed by Hobbs \etal.
(1990), for example; 
rather than directly equating the entities denoted by
the noun and the adjective, the relationship between the two, denoted 
above by $P$, is
underspecified.  However, in our approach, information from the qualia
structure provides
the instantiation.
In the case of {\bf telic-adjective}s, $P$ will be
instantiated by the telic predicate.

The lexical entry for {\it fast} can be specified as {\bf
adjective} with the semantics instantiated so that it can only be true of
an event.
Any particular instance of {\it fast} in an utterance will have to become
resolved to one particular subtype of {\bf adjective}.  
In the case of {\it fast typist}, the normal form of the adjective is ruled
out since {\it typist} is object denoting and only the telic role specifies
a possible predicate.  The choice of predicate may be determined by
selectional restrictions, which can be encoded in the LKB as constraints on
the types governing the predicate argument structure, but we will not
discuss the details here.  The qualia structure of the modified phrase is
equal to that of the noun -- see Figure~\ref{fasttypist}.
\begin{figure}
{\centering
\tiny
$\avmplus{\att{phr-sign}\\
    \attvaltlist{ORTH}{fast typist}\\
    \attval{SEM}{\avmplus{\attval{IND}{\ind{x}}\\
                          \attvaltyp{PRED}{and}\\
                          \attval{ARG1}{\ind{n}}\ \ 
                                      \avmplus{\attvaltyp{PRED}{typist}\\
                                      \attval{ARG1}{\ind{x}}}\\
                          \attval{ARG2}{\ind{a}}\ \ 
                                \avmplus{\attvaltyp{PRED}{and}\\
                                \attval{ARG1}{\avmplus{\attvaltyp{PRED}{fast}\\
                                                     \attval{ARG1}{\ind{e}}}}\\
                                \attval{ARG2}{\avmplus{\attval{PRED}{\ind{P}} \ \
\myvaluebold{type}\\
                                                     \attval{ARG1}{\ind{e}}\\
                                                     \attval{ARG2}{\ind{x}}}}}}}\\
    \attval{QUALIA}{\ind{q}}
                    \avmplus{\attval{TELIC}{\avmplus{\attval{PRED}{\ind{P}}\\
                                                     \attvaltyp{ARG1}{event}\\
                                                     \attval{ARG2}{\ind{x}}}}}\\
    \attval{DTRS}{\avmplus{\attval{HEAD-DTR}{\avmplus{\att{lex-count-noun}\\
                               \attvaltlist{ORTH}{typist}\\
                               \attval{SEM}{\ind{n}}\\
                               \attval{QUALIA}{\ind{q}}}}\\
                   \attval{COMP-DTRS HD}{\avmplus{\att{telic-adjective}\\
                               \attvaltlist{ORTH}{fast}\\
                               \attval{SEM}{\ind{a}}}}}}}$

}
\caption{FS for {\it fast typist} (letters are used here to indicate
reentrancy rather that the usual numbers to make the figure easier to follow).}
\label{fasttypist}
\end{figure}

In this formulation the qualia structure of the noun is not itself
directly modified by the adjective.  This differs from the treatment
we gave in Briscoe \etal. (1990) where, because we unified the entire
telic role into the representation of the modified nominal, all telic
events were, in effect, modified by the adjective.  This meant, for
example, that the interpretation of {\it enjoy the long book} entailed
that the reading event assumed was also {\it long}, which is not
necessarily correct.  In our current treatment, the variable is
specified by the adjective alone and this problem does not arise.

The interpretation of {\it fast typist} as someone who types fast is
defeasible.  In the context of a race between typists and accountants, for
example, a fast typist might be one who can run, ski or ride a motorbike
quickly; in this case the predicate is given contextually.
Briscoe \etal. (1990) argues for
the notion of a default lexical interpretation, which can be 
overridden in informationally rich contexts.
Lascarides \etal. (forthcoming) describes how persistent
default feature structures can be used to formalise this, by specifying the
portion of the semantic representation derived from the qualia structure as
default.

Our current treatment of {\it enjoy} is similar to that of {\it fast}, in that
the `coercion' is internal to the verb semantics. (Godard and Jayez (1993) also
adopt such an approach.)
We treat {\it enjoy} as having a type which can either be specialised to
take an event denoting complement in the usual way, or to introduce an
indirect relationship between an object and the event, which will be
instantiated via the telic role -- see Figures~\ref{enjoytypes} and
\ref{enjoyfig}.\footnote{We leave the treatment of
both {\it fast} and {\it
enjoy} with respect to coordination to \S5 below.}
\setlength{\unitlength}{0.8in}
\begin{figure}
\begin{picture}(6,1.5)(0,1.5)
\put(3,3){\makebox(0,0){\bf lex-enjoy-verb}}
\put(3,2.8){\makebox(0,0)[t]{\tiny $\avmplus{\attvaltlist{CAT SUBCAT}{v-or-np}\\
                                             \attvaltyp{SEM}{tvsem}}$}}
\put(2.9,2.5){\line(-4,-1){1.5}}
\put(3.1,2.5){\line(4,-1){1.5}}
\put(3,2.5){\line(0,-1){0.4}}
\put(1,2){\makebox(0,0){\bf coercing}}
\put(1,1.8){\makebox(0,0)[t]{\tiny $\avmplus{\attvaltlist{CAT SUBCAT}{NP}}$}}
\put(3,2){\makebox(0,0){\bf non-coercing-NP}}
\put(3,1.8){\makebox(0,0)[t]{\tiny $\avmplus{\attvaltlist{CAT SUBCAT}{NP}}$}}
\put(5,2){\makebox(0,0){\bf non-coercing}}
\put(5,1.8){\makebox(0,0)[t]{\tiny $\avmplus{\attvaltlist{CAT SUBCAT}{VPing}}$}}
\end{picture}
\caption{Outline of type hierarchy for {\it enjoy} and similar verbs}
\label{enjoytypes}
{\centering
\tiny
$\avmplus{\att{coercing}\\
          \attvallist{CAT SUBCAT}{\avmplus{\att{NP}\\
                                     \attval{SEM}{\ind{n}}\ \ 
                                            \avmplus{\attval{IND}{\ind{y}}}\\
                                     \attval{QUALIA TELIC PRED}{\ind{P}}}}\\
          \attval{SEM}{\avmplus{\attvaltyp{PRED}{and}\\
                                \attval{ARG1}{\avmplus{\attvaltyp{PRED}{enjoy}\\
                                                       \attvaltyp{ARG1}{e}\\
                                                       \attval{ARG2}{\ind{x}}\\
                                                       \attval{ARG3}{\ind{e'}}}}\\
                                \attval{ARG2}{\avmplus{\attvaltyp{PRED}{and}\\
                                                       \attval{ARG1}{\avmplus
{\attval{PRED}{\ind{P}}\\                                                       
 \attval{ARG1}{\ind{e'}}\\
 \attval{ARG2}{\ind{x}}\\
 \attval{ARG3}{\ind{y}}}}\\
                                                       \attval{ARG2}{\ind{n}}}}}}}$

}
\caption{Coercing form of {\it enjoy}}
\label{enjoyfig}
\end{figure}

One further example of an operation which can be
involved in constructional polysemy could be called {\it
broadening} since usages are available in context 
which appear to semantically subsume the basic sense.  
Usually it appears that a quale which is specified in the
basic sense becomes overridden in context.  
For example, the normal usages of {\it bank} and {\it cloud}
could be specified as stating both form and composition (earth / water vapour).
However, both have usages where alternative compositions are stated {\it bank of
rhodedendrons}, {\it bank of clouds}/{\it cloud bank}, {\it cloud of
mosquitoes}, {\it dust cloud}.   In some comparable cases the broadened sense may
appear more metaphorical, for example {\it forest of hands}.
In many cases there is evidence that broadening of meaning has
taken place diachronically and that the original senses tended to be specific and
concrete (see Sweetser 1990).  It seems appropriate to regard these examples as
being comparable to those given above in that there is a modulation of
sense rather than a complete shift, but unlike the cases discussed above, this
modulation is most naturally expressed as being non-monotonic.  For
example, in contrast with the
case of {\it reel} given earlier, there is a very strong preference for
one particular sense and the alternative interpretations are not
conventionalised, but given by context (there is no conventional
interpretation of {\it cloud} as {\it cloud of mosquitoes}).  This implies
that non-default interpretations will only be usual in contexts which
explicitly give the exceptional component (normally by compounding or
post-modification).
This then, is rather similar to
the situation with respect to the stereotypical readings of {\it enjoy the
book} and similar examples (Briscoe \etal., 1990).

To represent broadening
we make use of lexically specified persistent default components of the qualia
structure and allow these to be overridden. 
In the FS for the lexical entry for {\it cloud} shown in Figure~\ref{cloud}
the qualia structure
is stated to refer necessarily to an individuated physical object
of amorphous form, with a composition that is also physical and refers
cumulatively (i.e.~the composition 
is either a mass or a plural object).  By default, {\it
cloud} is a natural object (as opposed to an artifact) and is
composed of water vapour.\footnote{This description has been somewhat
simplified but in any case we would not claim that it
is completely adequate. 
It does not, for instance, cover the mass use of {\it cloud},
found in \exnum{+1}{a}, which seems to be available only with the
default usage (compare \exnum{+1}{b}):
\begin{ex}
\begin{subex}
We flew into dense cloud.
\end{subex}
\begin{subex}
* We walked into dense cloud of smoke.
\end{subex}
\end{ex}
Nor does it cover the metaphorical uses, such as {\it cloud of suspicion}.}
Referring to the process of overriding the lexically specified 
defaults as broadening is
perhaps somewhat misleading, since a more general FS never actually
exists in isolation according to this treatment.  The intuition that the
sense is broadened is reflected in 
the non-defeasible components of the modified structure, however:  for example
the semantic contribution of {\it cloud} to {\it cloud of mosquitoes} 
could be represented as a FS with unspecified composition.
\begin{figure}
{\centering
\tiny
$\avmplus{\att{lex-count-noun}\\
                  \attvaltyp{ORTH}{cloud}\\
                  \attvalshrunktyp{CAT}{noun-cat}\\
                  \attvalshrunktyp{SEM}{obj-noun-formula}\\
                  \attval{QUALIA}{\avmplus{\att{phys\_obj / natural\_obj}\\
                           \attval{FORM}{\avmplus{\att{nomform}\\
                                    \attvaltyp{RELATIVE}{indiv}\\
                                    \attvaltyp{ABS.}{amorph}}}\\
                           \attvaltyp{CONSTITUENCY}{phys\_cum / water-vapour}}}}$

}
\caption{Lexical entry for {\it cloud}}
\label{cloud}
\end{figure}

Broadening could alternatively 
be represented using a lexical rule which removes part of
the qualia structure.  But this is a less attractive account since it
would be difficult to avoid spurious ambiguity which would occur
if the broadened sense were specialised to have a
structure equivalent to the usual sense.  Furthermore, the default account
gives a natural explanation for the fact that explicit contextual specification
of the alternative compositions is necessary for the usage to be interpreted in its
broadened sense, which the lexical rule account would fail to capture, without some
additional mechanism.  In general, we see the use of lexical rules as
appropriate when there is a shift in syntactic or semantic type, as will be
illustrated in more detail in the next section.

\section{Sense extensions}
\label{sexts}

By contrast with constructional polysemy, we argue that there are
systematic polysemies which are best represented as lexical rules,
which we refer to as sense extensions; that is predictable creation of
different but related senses. 
As described in \S2, the formalism that we utilise to
express these rules is equally applicable to derivational processes, as
well as those of conversion, in that we treat all such lexical
processes as mappings between lexical (and occasionally phrasal)
signs.\footnote{This makes our approach closest to that of word-based
morphology (e.g.~Aronoff, 1976) but with the possibility of phrasal
based operations as well.} From our perspective, it is accidental that
some rules specify phonological modifications whilst others do
not.\footnote{In fact, there is more to be said on this topic, since
it seems plausible that derivational rules are less ambiguous, because
of the information about the process conveyed by the affix, and
therefore, perhaps more fine-grained in the sense modifications they
produce. Discussion of such differences though would take us outside
the scope of this paper.} However, we concentrate on cases which
involve little if any grammatical change, since these constitute the
major challenge to a uniform theory of lexical processes.

The examples of sense extension discussed below could be broadly
characterised as metonymic.  In Briscoe and Copestake (1991), we
suggested that similar mechanisms could be used to account for
metaphoric processes as well.  For example, the sense extension from
animals into metaphorical senses denoting humans with some particular
characteristic is apparently productive (e.g.~{\it John is a lamb /
pig / wombat}),
although the actual characteristics involved cannot be predicted from
knowledge of the animal sense.  We would argue, for example, that the
properties ascribed to a person by {\it pig} are stereotypical
associations with the animal, which would not be encoded in the qualia
structure.  Despite the more associative or analogical nature of
metaphorical sense extension, there is a core component to such
processes which should be expressed in terms of a sense extension
rule.  In general, we assume that the possible mappings defined by
sense extension rules define the limits to the possible shifts in
meaning, but more general reasoning may be involved in determining the
meaning more exactly in a particular context.  However, in this paper,
we will concentrate on metonymic examples.

\subsection{Grinding and portioning}
\label{grisec}

One process of sense extension is that which creates mass nouns
denoting an unindividuated substance from count nouns denoting an
individuated physical object of some kind.  Given the right context,
this process can apply quite generally.  The context normally
suggested is to imagine a large grinding machine, the Universal
Grinder (see, e.g.~Pelletier and Schubert, 1989), which would, for
example, turn {\it a table} into some substance that could be referred
to by the mass term {\it table}. 
Conventional subcases of grinding exist, for example,
food-denoting mass nouns can be formed from animal-denoting count
nouns (e.g.~{\it lamb}, {\it rabbit}, {\it haddock}, {\it chicken}).
This extension appears to be productive, at least in a sufficiently
marked context; for example, in the LOB corpus \exnum{+1}{} we find
the use of {\it mole} as a mass term.
\begin{ex} 
Badger hams are a delicacy in China while mole is eaten in many parts
of Africa. 
\end{ex}
We therefore cannot assume that the extended senses are listed
explicitly in the lexicon. As
in this example, where the animal sense is a count noun and the meat
sense is mass, sense extensions may affect syntactic
behaviour. However, the syntactic difference is not criterial since in
examples such as \exnum{+1}{} it is the predicate rather than the
complement which indicates that grinding has occurred.
\begin{ex}
Sam enjoyed the lamb.\footnotemark
\end{ex}
\footnotetext{Note
that in \exnum{0}{} both grinding and co-composition are required --
we assume that grinding of animals to meat creates an artifact which
is specified for eventive telic and agentive qualia, leading to a
default `Sam enjoyed eating the lamb' interpretation.} % numbering correct??
Furthermore, unlike the case of co-predication with constructional
polysemy, it seems much harder to coordinate predicates selecting for
the ground and unground senses of a complement, especially if this is
combined with co-composition, as \exnum{+1}{} illustrates.
\begin{ex}
\begin{subex}
?Sam fed and carved the lamb 
\end{subex}
\begin{subex}
??Sam fed and enjoyed the lamb
\end{subex}
\end{ex}
In \S5 we return to similar more acceptable cases and argue that in
restricted cases such examples are comprehensible as instances of
co-composition with the {\sc origin} specification of the ground
predicate. However, for the moment we assume that such examples
suggest that we have a genuine ambiguity, as opposed to vagueness: in
this case between animal and `animal stuff' denoting senses.

One striking similarity between conventionalised cases of grinding and
derivational processes is that both can be blocked (e.g.~Aronoff,
1976); that is, undergo preemption by synonymy or lexical form. For
example, Aronoff notes the pattern in \exnum{+1}{} and argues that
{\it gloriosity} is blocked by {\it glory}, whilst {\it curiosity} and
{\it curiousness} co-exist because they are not synonymous (possibly
as a result of semantic specialisation). 
\begin{ex}
\begin{subex}
curious / curiosity / curiousness
\end{subex}
\begin{subex}
glorious / *gloriosity / gloriousness
\end{subex}
\begin{subex}
His curiosity was attracted to the curiousness of the phenomenon
\end{subex}
\begin{subex}
??His curiousness was attracted to the curiosity of the phenomenon
\end{subex}
\end{ex}
Thus \exnum{0}{c} and \exnum{0}{d} are not equally acceptable because
{\it curiousness} is typically predicated of things, unlike {\it
curiosity} which seems more appropriate to people. Similarly, we find
the examples in \exnum{+1}{} with the conventionalised subcase of meat
grinding are odd.
\begin{ex}
\begin{subex}
?Sam ate pig (pork)
\end{subex}
\begin{subex}
?Sam likes cow (beef)
\end{subex}
\begin{subex}
`Hot sausages, two for a dollar, made of genuine pig, why not
buy one for the lady?.'\\
`Don't you mean pork, sir?' said Carrot warily, eyeing the glistening
tubes.\\
`Manner of speaking, manner of speaking,' said Throat quickly.
`Certainly your actual pig products. Genuine pig.'\\
(Terry Pratchett, 1989. {\it Guards, Guards!}, Gollanz, London. (p.~155,
Corgi edition, 1990))
\end{subex}
\begin{subex}
There were five thousand extremely loud people on the floor eager to
tear into roast cow with both hands and wash it down with bourbon
whiskey. (Tom Wolfe, 1979. {\it The Right Stuff}, Farrar, Straus and Giroux,
New York (p.~298, Picador edition, 1991))
\end{subex}
\end{ex}
Nevertheless, such examples do occur and when they do, as in
\exnum{0}{c,d} the intuition is that they are not synonymous with the
underived senses of {\it pork} and {\it beef}; they either convey a
negative attitude to the consumption of the meat on the part of the
speaker or an entailment of extended denotation, where more of the cow
or pig than is normally considered `meat' is being treated as food.
Blocking appears to be explicable on the basis of Gricean principles,
in particular the Maxim of Manner.  Given a choice between ways of
expressing the same meaning, the most easily interpretable ones should
be preferred.  
In general, this implies that common terms should be used rather than obscure
ones, briefer/simpler forms rather than more complex ones, and
unambiguous expressions instead of ambiguous ones.\footnote{Avoidance of 
ambiguity might apply to sense extension, but not to
derivation and it is not obvious how to measure brevity/complexity.  In
fact, blocking is explicable simply in terms of avoiding
obscurity, by which we mean that the speaker will generally 
use the form which has highest frequency. At first sight it might seem
that this is circular, but note that we are not trying to account for
the distribution of the blocked form in the general speech community here, 
but only for the effects on the individual speaker.  
Obviously the choices of individual
speakers affect overall frequencies, giving a positive feedback
effect in this case.
We consider this in more detail in \S6.}
Apparent violation
of this maxim carries the (discourse) implication that the terms are
not strictly synonymous, thus terms which are normally blocked will be
interpreted as carrying additional entailments (see Briscoe \etal., 1994
for additional discussion).

Nunberg and Zaenen (1992) point out that conventionalised subcases of
grinding vary cross-linguistically and that there are no clear
pragmatic explanations either for this variation or the absence of
some conventionalised cases in English. For example, they report that
in Eskimo (at least conventionalised) grinding of animals is
ungrammatical; and in English it seems that grinding of fruits or
nuts to produce liquids is not conventionalised: thus, the examples in
\exnum{+1}{} are awkward, though \exnum{+1}{b} is imaginable, for
example, in the context of a conversation between professional cooks.
\begin{ex}
\begin{subex}
?I drink pear rather than peach (cf. I drink orange for breakfast)
\end{subex}
\begin{subex}
?I fry courgettes with olive rather than safflower
\end{subex}
\end{ex}
For these reasons, they argue that a language specific system of
`lexical licenses' must be provided in order to specify which subcases
of the more general conceptual grinding transfer occur conventionally
in a particular language. In addition, different languages choose
different grammatical means to encode grinding and its subcases; for
instance, in Dutch meat grinding of animals is usually realised by
explicit compounding of {\it vlees} so lamb meat is {\it lamsvlees} and
so forth. The conversion process appears to be restricted to the more
stereotypical animals which are farmed for meat, such as chicken. In
this way, Dutch appears to somewhat mirror the situation in English
with liquid grinding, where certain sterotypical `juicy' fruit denoting nouns,
such as {\it orange} can acquire a juice sense through grinding, but
the majority require explicit compounding (e.g.~{\it apricot juice}).

Nunberg and Zaenen (1992) also argue that the meaning of ground
nouns is defeasible and therefore pragmatically specified. Thus, in
the case of grinding of animals, they would provide a lexical
license specifying that this is conventional in English, but argue
that the interpretation of ground animal denoting nouns as meat is
contextually specified. Thus, in \exnum{-1}{a,b} the Maxim of Manner
requires that we choose {\it pork} or {\it beef} because these terms
have a more restricted denotation than `animal stuff'. On the other
hand in examples such as \exnum{+1}{a,b} the context tells us that a more
restricted `meat' denotation is appropriate. Whilst, in
\exnum{+1}{c} the context tells us that a `fur' reading is more
appropriate, and in \exnum{+1}{d} that nothing more specific than
`stuff' is entailed.
\begin{ex}
\begin{subex}
Sam eats rabbit regularly
\end{subex}
\begin{subex}
Sam enjoyed the rabbit 
\end{subex}
\begin{subex}
Sam wears rabbit regularly
\end{subex}
\begin{subex}
Sam both wears and eats rabbit
\end{subex}
\end{ex}
Our approach is similar in that we posit a general abstract lexical
rule of grinding and conventionalised subcases, including animal meat
grinding and animal fur grinding. However, we also suggest that whilst
the more specific conventionalised `meat' and `fur' senses are
defeasible in appropriate contexts (because the more general ground sense
is also available), they are specified lexically as a
component of the conventionalised subcases of the grinding lexical
rule.

The general rule of {\psort grinding} is shown in
Figure~\ref{grinding} (using the type system described in
Copestake, 1992, which also discusses the formal semantic properties of the
grinding function in the context of the general treatment of mass terms
proposed by Krifka (1987)).  
The effect of the lexical rule is to create from a
count noun with the qualia properties appropriate to an individuated
physical object, a mass noun with properties appropriate for an
unindividuated substance.
\begin{figure}
{\centering
\tiny
$\avmplus{\att{grinding}\\
         \attval{0}{\avmplus{\att{lex-uncount-noun}\\
                  \attval{ORTH}{\ind{0}}\ \ \myvaluebold{orth}\\
                  \attvalshrunktyp{CAT}{noun-cat}\\
                  \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                           \attval{IND}{\ind{1}}\ \ \boxvaluebold{obj}\\
                           \attval{PRED}{\ind{2}}\avmplus{\att{modified-pred}\\
                                                \attvaltyp{MODIFIER}{grinding}\\
                                                \attval{MODIFIED}{\ind{3}}\ \ \myvaluebold{string}}\\
                           \attval{ARG1}{\ind{1}}\\
                           \attvaltyp{PLMOD}{false}\\
                           \attvaltyp{QUANT}{false}}}\\
                  \attval{QUALIA}{\avmplus{\att{physical}\\
                           \attval{AGENTIVE}{\avmplus{\att{agentive}\\
                                    \attval{ORIGIN}{\ind{3}}}}\\
                           \attval{FORM}{\avmplus{\att{nomform}\\
                                    \attvaltyp{RELATIVE}{mass}}}}}}}\\
         \attval{1}{\avmplus{\att{lex-count-noun}\\
                  \attval{ORTH}{\ind{0}}\\
                  \attvalshrunktyp{CAT}{noun-cat}\\
                  \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                           \attval{IND}{\ind{4}}\ \ \boxvaluebold{obj}\\
                           \attval{PRED}{\ind{3}}\\
                           \attval{ARG1}{\ind{4}}\\
                           \attvaltyp{PLMOD}{false}\\
                           \attvaltyp{QUANT}{true}}}\\
                  \attval{QUALIA}{\avmplus{\att{physical}\\
                           \attval{FORM}{\avmplus{\att{nomform}\\
                                    \attvaltyp{RELATIVE}{individual}}}}}}}}$

}
\caption{Grinding}
\label{grinding} 
\end{figure}

We specialise the grinding rule to allow for cases such as the
animal/meat extension explicitly.  The typed framework provides us
with a natural method of characterising the subparts of the lexicon to
which such rules should apply.  The lexical rules can, in effect, be
parametrised by inheritance in the type system.  For example, we can
give rules which inherit information from {\psort grinding} such as
{\psort meat-grinding}:
\begin{laureldesc}
meat-grinding\\
\> \verb+< > < grinding < > +\\
\> \verb+< 1 QUALIA > =+ {\bf animal}\\
\> \verb+< 0 QUALIA > =+ {\bf c\_subst}.
\end{laureldesc}
As in \S\ref{lrules} {\bf c\_subst} is a type which stands for normally
comestible naturally
derived substances.  
The lexical rule can be applied to the lexical entry for {\it rabbit}
to generate a sense corresponding to `edible
stuff derived from rabbits' partially represented as shown in
Figure~\ref{groundrabbit}.  Here the specification of the value for
the telic role arises from the constraint on the type {\bf
c\_subst}.  Using the notion of persistent defaults described in Lascarides
{\it et al} (forthcoming), we can treat this as defeasible.
\begin{figure}
{\centering
\tiny
$\avmplus{\att{lex-uncount-noun}\\
         \attvaltyp{ORTH}{rabbit}\\
         \attvalshrunktyp{CAT}{noun-cat}\\
         \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                  \attval{IND}{\ind{0}}\ \ \boxvaluebold{obj}\\
                  \attval{PRED}{\avmplus{\att{modified-pred}\\
                                       \attvaltyp{MODIFIER}{grinding}\\
                                       \attval{MODIFIED}{\ind{2}}\ \ \myvaluebold{rabbit\_1}}}\\
                  \attval{ARG1}{\ind{0}}\\
                  \attvaltyp{PLMOD}{false}\\
                  \attvaltyp{QUANT}{false}}}\\
         \attval{QUALIA}{\avmplus{\att{c\_substance}\\
                  \attval{AGENTIVE}{\avmplus{\att{agentivestuff}\\
                           \attval{ORIGIN}{\ind{2}}}}\\
                  \attvaltyp{TELIC PRED}{/consume}\\
                  \attval{FORM}{\avmplus{\att{nomform}\\
                           \attvaltyp{RELATIVE}{mass}}}\\
                  \attval{OBJECT-INDEX}{\ind{0}}}}}$

}
\caption{Meat/flesh sense of {\it rabbit}}
\label{groundrabbit}
\end{figure}
The {\psort meat-grinding} rule creates a second extended sense for
the mass noun {\it rabbit} (and other animal denoting count nouns) but
does not result in the full specification of what might usually be
taken as the meaning of the meat/flesh sense.  The substance is stated
to be edible (to be precise, to have the normal purpose of being eaten)
and to be derived from the animal, but there is no
attempt at defining the meaning to exclude, say, stuff derived from bones;
particular cultural assumptions will affect exactly what
is taken to be edible, so {\it rabbit} will usually
exclude the bones but {\it whitebait} will not, for example.  Thus not
all the characteristics are captured by the lexical rule and we assume
that pragmatic effects will ensure further contextual specialisation.

The more specific rules which inherit from the general grinding rule,
express the conventionalised processes that apply to semantically
specified parts of the lexicon.  In addition to {\psort meat-grinding}
we could also define a lexical rule which gives the fur/skin sense,
available for {\it rabbit}, {\it mink}, {\it beaver}, {\it calf}, {\it
lizard}, {\it crocodile} and so forth.  In this way we account for the
possibility of multiple distinct mass senses being possible.  In
context, a general mass sense corresponding to the application of the
underspecified grinding rule is available, as in \exnum{+1}{}.
\begin{ex}
After several lorries had run over the body, there was rabbit
splattered all over the road.
\end{ex}
Thus, under this account, the defeasibility of the more specific sense
is predicted in terms of ambiguity. The alternative of relying on
pragmatic specification of a single underspecified sense seems to us
less satisfactory because of the specificity of readings found in
uninformative contexts; for example, in examples such as \exnum{-1}{b}
or \exnum{+1}{}, the natural interpretation is that the rabbit was
eaten. 
\begin{ex}
Sam enjoyed but later regretted the rabbit
\end{ex}
Under the co-compositional account of such constructional polysemy
(see \S3) this is straightforward since the {\it meat-grinding}
sense of {\it rabbit} provides a telic role which allows the
eating interpretation to be constructed.\footnote{We defer to \S6 an
explanation of why this reading is preferred to one in which Sam is
wearing rabbit fur.} However, if the lexicon does not propose such a
sense, it is unclear what it is about the context which allows
pragmatic specialisation of the interpretation. Briscoe \etal. (1990)
provide empirical support for the hypothesis that the lexicon proposes
and pragmatics disposes of such initial interpretations: on the assumption
that logical metonymy will be utilised when a reading based on qualia
is appropriate, or when the context is rich enough to provide
determinate information to override this `default'; and that an
explicit event will be specified where a non-default reading is
appropriate, but the general context is not rich enough to override the
default. Thus, a verb like {\it enjoy} occurs mostly with metonymic NP
complements, but when it does occur with progressive VPs the
interpretation is never that which would be predicted by
co-composition with eventive qualia; whilst with metonymic NP
complements, where the default reading is inappropriate the context is
always informationally rich and determinate. 

Multiple sense extensions / lexical rules may be applied in sequence.
For example, we mentioned in \S\ref{lrules} the lexical rule
{\psort portioning} which converts food or drink denoting mass nouns
into count nouns denoting a portion of that substance (e.g.~{\it three
beers}).  This is clearly productive,
it can be used with names of particular types of beer, for instance,
such as {\it three Heinekens/IPAs/Anchor Steams}.  
It can also apply to extended senses such
as {\it three lambs}, at least in the context of a restaurant. This
`feeding' of lexical rules raises the issue of why ground portioned
nouns are not, for instance, reground creating an infinite sequence of
more and more derived senses. There are several potential solutions to
this problem; one might be to set up the rules so that grinding feeds
portioning but not vice-versa. However, we do not think that this is
necessary, and in fact there is no reason to believe that portioned
count nouns are of a type inaccessible to grinding. Rather we think
that the non-existence of ground portioned nouns follows from the
semi-productivity of lexical rules; the ground portioned sense is
synonymous with the original mass sense and is thus blocked.
We return to the issues of semi-productivity and blocking in \S6.

\subsection{Nominal Metonymies}

Grinding can be characterised as a set of metonymic sense extensions
in which the animal comes to stand for something derived from the
animal. However, it appears to have a different flavour to many of the
nominal metonymies identified by Nunberg (1979), for example. Many of
these involve objects standing for people, as in \exnum{+1}{}.
\begin{ex}
\begin{subex}
The third violin is playing badly
\end{subex}
\begin{subex}
The Armani suit lounging gracefully at the bar looks bored
\end{subex}
\begin{subex}
London said that a new passport could not be issued
\end{subex}
\begin{subex}
The village voted conservative at the last election
\end{subex}
\end{ex}
Although these putative sense extensions seem to have no grammatical
effects, sometimes they can affect agreement. Nunberg (1979) and
Pollard and Sag (in press) discuss the use of food to denote people, which
is a less conventionalised example of a similar metonymy, as in
\exnum{+1}{}. 
\begin{ex}
\begin{subex}
The ham sandwich wants a coke
\end{subex}
\begin{subex}
The french fries is getting impatient
\end{subex}
\end{ex}
It is clear that agreement in \exnum{0}{b} is determined by the
referent rather than the syntax of the NP {\it french fries} which
would induce plural agreement given a non-metonymic reading.
Similarly, co-predication of such examples seems awkward, as in
\exnum{+1}{}. 
\begin{ex}
\begin{subex}
??The ham sandwich wants a coke and has gone stale
\end{subex}
\begin{subex}
??The french fries is getting impatient and are getting cold
\end{subex}
\begin{subex}
??The third violin is scratched and playing badly
\end{subex}
\begin{subex}
??The Armani suit is at the bar and crumpled
\end{subex}
\end{ex}
Similarly, it is clear that pronominal agreement and reflexivisation
are also affected by transfer of reference (Fauconnier, 1985; Nunberg,
1993; Pollard and Sag, in press).  These observations suggest to us
that these nominal metonymies must have a non-pragmatic component and
must be treated as distinct senses / signs.  Within our framework, we
propose to treat them as sense extensions and provide lexical rules
for them, analogous to those developed for grinding and portioning.

Another such sense extension is that from a word denoting a fruit (or
nut) to a plant bearing that type of fruit (e.g.~{\it apple}, {\it
gooseberry}, {\it walnut}) which is found in Italian and Spanish as
well as English.\footnote{Some techniques for exploiting parallelism
between lexical processes in machine translation are described in
Copestake and Sanfilippo (1993).}  However, in the Romance languages
the fruit is usually (but not always) feminine while the tree is
masculine (there are one or two exceptions).  For example, in Spanish
we have {\it aceituna}/{\it aceituno} (olive), {\it pomelo}/{\it
pomelo} (grapefruit) (see Soler and Marti, 1993). In a few cases, the
suffix {\it ero} applies -- {\it albaricoque}, {\it albaricoquero}
(again illustrating the similarity of sense extension, conversion and
derivation). The basic type for the lexical rule can be stated as:
\begin{laureldesc}
{\bf fruit-to-tree} ({\bf lexical-rule})\\
\> \verb+< 1 > =+ {\bf lex-count-noun}\\
\> \verb+< 0 > =+ {\bf lex-count-noun}\\
\> \verb+< 1 QUALIA > =+ {\bf c\_nat\_obj}\\
\> \verb+< 0 QUALIA > =+ {\bf plant}.
\end{laureldesc}
The normal lexical rule for Spanish can then be stated as:
\begin{laureldesc}
fruit-to-tree-ESP\\
\> \verb+<> =+ {\bf fruit-to-tree}\\
\> \verb+< 0 SEM IND AGR GENDER > =+ {\bf masc}\\
\> \verb+< 1 QUALIA AGENTIVE ORIGIN > = < 0 SEM PRED >+ .
\end{laureldesc}
The exceptional cases can be stated using explicit lexical entries
which override the usual results of lexical rule
application:
\begin{laureldesc}
higuera\\
\> \verb!<> < ( higo + fruit-to-tree-ESP ) <>!\\
\> \verb+< SEM IND AGR GENDER > =+ {\bf fem}.
\end{laureldesc}
This example illustrates that some nominal metonymies, just like
grinding, can have different grammatical encodings in different
languages and this supports our contention that such processes should
be treated as language specific lexical rules, creating lexical
entries (signs) with extended senses and different grammatical and/or
phonological specifications, as required. We return to the issue of
how to distinguish such cases from those of sense modulation or
constructional polysemy in \S5.

\subsection{Phrasal sense extension}
\label{phrse}

There are some examples where sense extensions apparently apply to phrases.
Thus the place {\tt ->} group sense extension applies both to
words such as {\it village} and place denoting phrases, as in \exnum{+1}{}.
\begin{ex}
\begin{subex}
The south side of Cambridge voted Conservative
\end{subex}
\begin{subex}
Three villages / three villages south of the river /
?three villages built of stone voted for the proposed ban on timber production.
\end{subex}
\end{ex}
These seem quite restricted; in this particular sense extension
it appears that only modifiers which might apply to the group of
people, or which are locational (as in {\it the south side of
Cambridge}) are fully acceptable. With grinding too, there are cases of
phrases, or at least compounds, undergoing the sense extension, as in
\exnum{+1}{}. 
\begin{ex}
Here you can eat alligator tail, elk, rattlesnake and that
snicker-inspiring delicacy, Rocky Mountain oysters. (CSAA magazine)
\end{ex}
The treatment of such phrasal sense extensions in the LKB is a
straightforward generalisation of the lexical case since 
as we described in \S\ref{lrules} `lexical'
rules can apply to any feature structure representing a lexical or
phrasal sign with the appropriate properties.  

Some examples where a sense extension apparently applies to a phrase
are misleading though, since the availability of qualia structure does
allow for modifiers which apply to the unextended sense.  For example,
in the meat grinding cases, we get {\it corn-fed chicken} and {\it
young lamb}, where the adjectival phrase, on semantic grounds, has to
apply to the animal, not the meat, but we also get, for example, {\it
young veal}, {\it corn-fed beef}, so such examples do not demonstrate
that grinding is applying to a phrase.  We would analyse all these
cases as ones in which the modifier is applying to the {\feature
origin} feature of the qualia structure (see Figure~17 and the example
of {\it fast typist} shown in Figure~\ref{fasttypist}, and also
\S5).\footnote{Many adjectives which could normally apply to the animal 
but which are not usually seen as affecting the meat do not appear in
these constructions ({\it ??We serve happy/beheaded chicken} vs. {\it
We serve the meat of happy/beheaded chickens}; see Nunberg, this
volume.)  However, we think this is explicable on the basis of general
pragmatic principles outlined in \S5, below.}

\subsection{Novel sense extensions}

Pragmatic factors clearly affect the acceptability of the
underspecified, unconventionalised uses of sense extension typified by
the `ham sandwich' example in \exnum{-1}{a}.  Something like Nunberg's
(1979) conditions on transfer of reference are needed for the intended
referent to be identifiable.  But these in themselves do not
sufficiently delimit the possible uses of even the novel sense
extensions.  Nunberg postulates a set of basic transfer functions ---
we would identify these with our most general sense extension rules.
The existence of a (unidirectional) object {\tt ->} human basic
transfer function allows for the ham sandwich sentences, in
appropriate contexts, but the converse case does not seem to be
possible.  Thus, for example, \exnum{+1}{} is an unacceptable way of
referring to the food that has been ordered by an identified customer.
\begin{ex}
\mbox{}* The man with the brown suit is in the microwave.
\end{ex}
Nunberg discusses the cue-validity of such putative transfer functions
and argues that those which occur are motivated by the value of the
function as a determinant of the referent. However, {\it a priori}
there is no apparent reason why the function from human {\tt ->}
object cannot apply in contexts in which \exnum{0}{} might be uttered.

For the ham sandwich examples the basic sense extension rule that
applies could be characterised as physical object {\tt
->} human.  It seems reasonable to assume that such a rule is
analogous to the basic grinding rule (see \S\ref{grisec})
in that it is generally possible only in marked
contexts, but that there are conventional subcases.  For example,
Atkins (1990) lists:
\begin{quote}
characteristic dress {\tt ->} person who wears it (e.g.~{\it blackshirt},
{\it red beret})\\
musical instrument {\tt ->} person who plays it (e.g.~{\it cello}, {\it
sax}).
\end{quote}
(Some dictionaries also list, for example, {\it spear}, {\it bow}, {\it
gun} meaning people who use these weapons, but these seem somewhat archaic.)

Thus we would treat the interpretation of all such novel examples in
much the same way as the conventional cases.  Novel extended usages
are not rare, at least in some styles of writing; \exnum{+1}{} is
taken from a newspaper travel article.
\begin{ex}
[Chester] serves not just country folk, but farming, suburban and city
folk too.  You'll see Armani drifting into the Grosvenor Hotel's exclusive
(but exquisite) Arkle Restaurant and C+A giggling out of its streetfront
brasserie next door. (Guardian Weekly, 13 November 1993)
\end{ex}
Here {\it Armani} and {\it C+A} are presumably intended to be
interpreted along the lines of {\it people wearing clothes from Armani
/ C+A} (and could be analysed as a combination of two conventionalised
processes, brand name {\tt ->} object, plus characteristic dress {\tt
->} person who wears it).\footnote{It seems relatively easy to become
accustomed to metonymic usages after a particular pattern when they
recur in some corpus as though the process were becoming (locally)
conventionalised (ham sandwich examples may have this status in the
linguistics literature).}  Our account predicts that all such novel metonymic
sense extensions should be analysable as falling into a range of basic
patterns which might themselves be language dependent. These basic
rules whether conventionalised or not should interact with other
grammatical rules appropriately; for example, grammatically induced
type coercion occurs when NPs appear as predicative complements, as in
\exnum{+1}{} (see e.g.~Partee, 1992).
\begin{ex}
\begin{subex}
Sam considers Bill a fool
\end{subex}
\begin{subex}
Sam is a fool
\end{subex}
\end{ex}
In \exnum{0}{} {\it a fool} is coerced from a generalized quantifier
to a property (from $\langle\langle e, t\rangle, t\rangle$ to $\langle e,
t\rangle$ in extensional terms). Ham sandwich examples can
participate in this coercion quite easily, as in \exnum{+1}{} said to
a waiter delivering a variety of dishes.
\begin{ex}
I am the ham sandwich
\end{ex}
This is compatible with our account, given that the sense extension
will produce a meaning which can be glossed as `the x who ordered a ham
sandwich' which can in turn be coerced to a property of ordering a ham
sandwich by the standard type shifting operator.

\subsection{Directionality}

Although in the case of derivation there is clear evidence of
directionality, this is not the case with conversion.  In the cases
with which we are most concerned where the process is still clearly
productive, novel uses, such as the example of {\it mole} given
earlier, at least demonstrate that a particular directionality is
possible.  In some cases, the basic sense is evident from the
morphology, thus we assume that the fruit/nut sense rather than the
bush/tree sense is primary in {\it gooseberry}, {\it strawberry}, {\it
walnut}, {\it chestnut} and so forth.
This does not preclude the
possibility that the direction might change over time 
nor that there might be cases analogous to
morphological back formation. In other cases, there are closely
related rules of derivation or compounding which suggest that there
should be the same directionality in the conversion case; for
example, compounding with {\it juice} and {\it meat} closely mirrors
the grinding conversion, whilst {\it -ful} suffixation mirrors the
container/contents nominal metonymy. In addition, the tests for
cue-validity of transfer functions which Nunberg (1979) proposes can also be
used to distinguish basic from metonymic senses, as he suggests, and
there appear to be general constraints on transfer functions which
suggest that they extend from the concrete to the abstract and the
simple to the complex (e.g.~Sweetser, 1990).

Cruse (1986:69) describes a test for distinguishing senses according to
whether or not they are 
fully established (i.e.~conventionalised in our terminology).
This involves the possibility of simultaneously
negating the non-fully-established sense whilst asserting the 
fully established sense, while
the converse is much less acceptable.  Thus, his example of {\it
novel} meaning the text or the physical object is given in
\exnum{+1}{}.
\begin{ex}
\begin{subex}
I'm not interested in the binding, cover, typeface etc --- I'm interested
in the novel.
\end{subex}
\begin{subex}
? I'm not interested in the plot, characterisation etc --- I'm interested
in the novel.
\end{subex}
\end{ex}
It is reasonable to assume that the perceived directionality of sense
extension processes would be from fully conventionalised to less
conventionalised senses.
The examples in \exnum{+1}{} seem to confirm the
intuition that the animal sense is primary, in cases of meat grinding,
and the fruit sense in the fruit tree examples.
\begin{ex}
\begin{subex}
I don't want the meat, I want the lamb.
\end{subex}
\begin{subex}
?I don't want the animal, I want the lamb.
\end{subex}
\begin{subex}
I don't want trees, I want peaches.
\end{subex}
\begin{subex}
? I don't want fruits, I want peaches.
\end{subex}
\end{ex}
The behaviour in this test is explicable on the assumption that basic
conventional senses are assumed by default, and that the extended
senses have to be forced by context. Their are some cases where
neither Cruse's test nor any of the other criterion mentioned
give clear results.  Nunberg (1978) discusses at length the difficulty
of making such a choice in the case of the instance/type distinction,
for example. The directionality of sense extension rules does not
affect the representation of the signs involved
so these preferences in
interpretation must follow from the manner of rule application. In
\S6, we argue that the semi-productivity of such rules can also be
used to predict these preferences.

\section{Coordination and co-predication}

Given that we have suggested two different methods for dealing with
systematic polysemy, it is clearly necessary to establish that we can,
in fact, distinguish between constructional polysemy and sense
extension.  It is not always straightforward to distinguish between cases
where the relational approach of encoding the different aspects of one
entity will work and the examples where it seems necessary to
postulate the construction of a new structure via the lexical rule
mechanism.  Pustejovsky (1994) suggests that the distinction can
be made on the basis of co-predication: that {\it door} can be treated
as having a relational structure encoding both the aperture and
physical object usages, because of the acceptability of
\exnum{+1}{}.
\begin{ex}
John painted and walked through the door.
\end{ex}
However, he argues {\it newspaper} must be coerced between the
physical object and organisation usages because of the unacceptability
of \exnum{+1}{a}, despite the acceptability of examples such as
\exnum{+1}{b} which might be the result of a
coercion process applying phrasally to the NP. \footnote{In this
particular case, however, it is by no means obvious that {\it the
newspaper that you are reading} has to refer to a physical copy of a
paper (see below).}
\begin{ex}
\begin{subex}
\mbox{}* The newspaper fired its editor and fell off the table.
\end{subex}
\begin{subex}
John used to work for the newspaper that you are reading.
\end{subex}
\end{ex}

This is an area where opinions (and judgements) differ.  
For example, Cruse (1986:65) treats
{\it door} as having distinct panel and aperture senses
on the basis of the semantic abnormality of
\exnum{+1}{}:
\begin{ex}
? We took the door off its hinges and then walked through it.
\end{ex}
but assumes that a `global door' sense is involved in \exnum{+1}{} (which
was cited by Nunberg (1979) as evidence that {\it door} is not ambiguous).
\begin{ex}
The door was smashed in so often that it had to be bricked up. 
\end{ex}
Care also has to be taken to use cases where the
predicates could be true of the same entity, thus \exnum{+1}{}
does not demonstrate that {\it teacher} must be coerced.  
\begin{ex}
? The teacher was pregnant and had a beard.
\end{ex}
We can assume that acceptable examples of co-predication are evidence
that a single structure is available, and thus that constructional
polysemy is at work. However, we will argue that zeugma\footnote{Zeugma is
the traditional term for
the variety of anomaly which arises when terms are inappropriately linked
(yoked) together, such as in \exnum{+1}{}:
\begin{ex}
He was wearing a scarf, a pair of boots, and a look of considerable
embarrassment. (from Cruse, 1986:13) 
\end{ex}}
is not in general
explicable on the basis of the existence of multiple 
distinct lexical structures.  So we
cannot necessarily take negative
examples as evidence for distinct senses and thus as supporting an account
involving sense extension as
opposed to constructional polysemy.

In the cases where we have posited rules of sense extension, it is
encumbent on us to account for apparent counter-examples involving
co-predication. The clearest such examples are coordinations, where
there is no possibility of arguing that the sense extension applies
phrasally and where the standard rule of coordination requires type
compatibility (e.g.~Partee, 1992). Furthermore, coordinations
involving sortal mismatches are often zeugmatic, as \exnum{+1}{}
illustrates. 
\begin{ex}
\begin{subex}
He arrived in a Rolls Royce and a temper
\end{subex}
\begin{subex}
Our office typist is fast and bearded
\end{subex}
\end{ex}
Although we argued that similar co-predications of ground and unground
senses seem to be ruled out in \S4.1, some appear to be possible. For
example, \exnum{+1}{a} involves a coordination of predicates which
select the animal sense of {\it chicken}, whilst in \exnum{+1}{b} we
appear to have one which selects both animal and meat senses.
\begin{ex}
\begin{subex}
This chicken is corn-fed and healthy
\end{subex}
\begin{subex}
Corn-fed and inexpensive chicken is difficult to find
\end{subex}
\end{ex}
We can account for both these examples
on the assumption that the {\sc origin} of the qualia structure of the
ground sense is available for modification (as mentioned in \S4.3).
Nunberg (this volume) argues that this treatment is
insufficiently restrictive since
the
property described has to have some applicability to the meat for the
predication to be fully acceptable.  However we would argue that
examples such as \exnum{+1}{a} are no different from those in which a
contextually unexpected adjective is applied straightforwardly to the
noun, for example, \exnum{+1}{b}:
\begin{ex}
\begin{subex}
?? We serve corn-fed and happy chicken
\end{subex}
\begin{subex}
? We serve dense potatoes
\end{subex}
\end{ex}
\exnum{0}{b} is odd, despite the fact that potato tubers can differ in
physical density, since it is not generally realised that this affects
eating quality.  Thus, on our account, both these examples are problematic
simply because the context is not providing/supporting a clear
interpretation.  Making the context explicit improves the
acceptability, since it restricts and guides the possible
interpretations.  Such effects are, admittedly, more likely to arise
with adjectives that modify different qualia on our account, but this
would be expected, since properties true of aspects of an entity are
less likely to relate to a common property, and thus be part of a
coherent discourse.

\subsection{Coordination in constructional polysemy}

In \S\ref{fast} we described a representation of adjectives which
relied on selection of predicates from the qualia structure according to
the type of the resolved adjectival structure.
Adjectives of the same or differing types can be coordinated, although
there seem to be some restrictions on the productivity of this process when
the adjectives select different qualia (?{\it fast and well-dressed typist}).
But some examples are more acceptable, such as {\it fast and intelligent
typist} where {\it intelligent} is assumed to be true of the unmodified variable,
and the oddness of the others is perhaps better explained as a
pragmatic effect.  We will assume that the {\sc subcat} value of the conjoined
phrase is the unification of the values on the adjective daughters and that
the semantics is simply specified as the conjunction.\footnote{We will
also assume, for the moment, that the type of the conjoined phrase is
underspecified.  
Technically, this raises a problem analogous to that affecting 
conjunction in HPSG (Pollard and Sag, in press), since the type could not
be fully resolved, although, in this particular 
case, it is possible to define a more complex
type system which avoids this situation.}
Thus we have:
\[ [ x ] [ fast (e) \wedge P (e, x) \wedge intelligent (x) ]
\]
where P is coindexed to the telic predicate of the subcategorised noun.
This can be applied to {\it typist} to give 
\[ [ x ] [ fast (e) \wedge type (e, x) \wedge intelligent (x)
\wedge typist (x) ]
\]
Cases such as {\it corn-fed and expensive chicken} are similar, on the
assumption that {\it corn-fed} selects the {\feature origin} in this instance.

Coordination of the noun raises some more complex issues.  The first point to
notice is that the treatment of adjectives given above precludes the
possibility of selecting one role from one conjunct and a different one
from another.   This appears to be basically correct for adjectival modification.  
In the example below,
{\it lap} is event denoting and the normal form of {\it fast} would be 
expected to apply,
whereas it selects for the telic role of {\it cars}.
\begin{ex}
??Prost only gets enthusiastic about fast cars and laps.
\end{ex}
This is odd at least on the 
reading in which {\it fast} applies to the conjunction {\it cars
and laps}. 
However, cases where the adjective selects for the same role appear to be
generally acceptable, even if the predicate selected differs.  For example:
\begin{ex}
The company's fast typists and computers have raised productivity by 20\%.
\end{ex}
In such examples, the conjoined entities should be
regarded as being combined to produce a single (complex) entity, in order
to get the collective readings.

The conjoined form {\it typists and computers} can be constructed from the
individual representations using,
for example, the formalism described by 
Link (1983) to structure the domain such that complex entities can be described.
Thus, the
semantics of the conjoined phrase could be written as:
\[ [ x \iplus y ] [ typist (x) \wedge computer (y) ] \]
Given the approach that we have adopted previously, of treating the
qualia as quite distinct from the rest of the sign, the most
straightforward option for the qualia of the conjunction is to
identify it with the disjunction of the qualia of the
conjuncts.\footnote{The main reason why we have maintained the
distinction between qualia structure and the rest of the sign here is
to avoid making the representations unnecessarily theory dependent.
Within HPSG, for example, there are a variety of ways in which the
qualia structure might be incorporated into the semantic
representation, which would affect the way in which the qualia
structure of the conjunct was derived.  Qualia could be regarded as
part of the {\feature background} (that is as presuppositional rather
than truth conditional) or even be located on the {\feature index}
(Pollard and Sag, in press).  These options would carry different
implications as to how the qualia should be combined in conjoined
phrases.  The only essential point here is that the interpretation of
examples like {\it fast typists and computers} where {\it fast}
distributes over the conjuncts requires that the qualia structure of
the conjuncts should still be individually accessible in the phrase.}
In this case, {\it fast} would select the predicates from the
disjunct, giving:
\[ [ x \iplus y ] [ fast (e) \wedge ( compute \vee type )( e, x \iplus y )
\wedge typist (x) \wedge computer (y) ] \]
But we may want to be able to deduce from this a
distributive reading which associates the correct predicate with the
particular type of individual (typists who type fast and computers which
compute fast).  
To do this, we would have to complicate the representation somewhat, so
that the disjunction was not simply of atomic predicates, but restricted the
arguments with respect to the qualia.
Although we do not want to equate the fast event with the variables in the
qualia structure, we could restrict the fast event to be a
subevent of those specified there.  In the case of the disjunctive qualia,
this would have the effect of restricting fast typing events to the typists and
fast computing events to the computers.  We will leave this
open, since the precise formulation depends on the semantics adopted for
events and there are other options, involving alternative treatments of
the relationship of the qualia structure to the rest of the sign.

Our current proposal for the representation of verbs like {\it enjoy},
{\it begin} and so on, discussed in \S\ref{fast}, involves treating
them in a manner analogous to {\it fast}.  Conjunctions such as those
in \exnum{+1}{} are thus possible in much the same way as the
conjunction of {\it fast and intelligent}.
\begin{ex}
\begin{subex}
Sam picked up and finished his beer
\end{subex}
\begin{subex}
Sam ate and enjoyed the caviar
\end{subex}
\begin{subex}
Sam wrote but later regretted that article
\end{subex}
\end{ex}
However, unlike modification by {\it fast}, there are some cases where the
complement to {\it enjoy} is a conjunction, such that one conjunct is
object denoting and another event denoting.
\begin{ex}
\begin{subex}
I enjoy films and mending antique clocks
\end{subex}
\begin{subex}
We found Sam swimming the channel, which he enjoys more than golf (due
to Geoff Nunberg)
\end{subex}
\begin{subex}
Gordon Parry (Gary Mavers) has come into the world and enjoys a small car,
many women possibly including Julia and embezzling the premiums he collects
(Guardian, 16th Jan 1990, Features)
\end{subex}
\end{ex}
In any approach where the `coercion' is internal to {\it enjoy},
problems arise in treating such examples, No straightforwardly
unification based approach can account for both \exnum{-1}{} and
\exnum{0}{} by postulating one operation applying either to the verb
or its complement.  If coercion applied to the noun phrase then the noun
would need to have a dual coerced/uncoerced nature in \exnum{-1}{}, if
it were internal to the verb then this would have to be both coercing
and non-coercing in \exnum{0}{}.  This remains true even if the work of
specifying the coerced meaning is shared between the components, or if
the coercion affects part of the sign rather than the whole of it.

Since the examples of conjunction of unlike types in the
complement seem more restricted and marked than the conjunction of the
verbs, we prefer our current account (which makes \exnum{0}{} problematic
rather than \exnum{-1}{}) over the one we gave in Briscoe \etal. (1990)
(where the converse applied).
The difficulty seems comparable
to the problem of cross-categorial coordination from a syntactic viewpoint
for which a number of solutions have been proposed
(see e.g.~Sag \etal., 1985; Shieber, 1992; Cooper, 1991).  
Conjunction is licensed in examples such as \exnum{+1}{} if the
syntactic descriptions of each of the conjuncts independently unifies with
the subcategorisation requirement of the verb, despite the fact that these
descriptions will not unify with each other: 
\begin{ex}
Tigger became famous and a complete snob
\end{ex}
Similar remarks must apply to the syntax of examples such as \exnum{-1}{}
and the semantic effects parallel the syntactic ones: the conjuncts
individually have types which are accepted by {\it enjoy} and the
conjunction is only licensed in contexts where {\it enjoy} (or a similar
predicate) is involved.  So a promising direction for future research would
be to provide an account where this parallelism is explicit.  However, any
such account will have to move beyond a strictly unification based
formalism, to allow for the multiple distinct coercions involved in
examples such as \exnum{-1}{c}. 

\subsection{Co-predication tests}
\label{newspaper}

There are cases where the co-predication test gives less clear
indications as to whether constructional polysemy or sense extension
are involved.  Take the example of {\it book}: it seems clear enough
that it has two senses (or usages) --- as a physical entity which
represents some text and as the abstract text itself.  But the
distinction between these is not really straightforward.  Consider the
set of examples in \exnum{+1}{}
\begin{ex}
That book is full of metaphorical language.\\
That book is full of long sentences.\\
That book is full of spelling mistakes.\\
That book is full of typographic errors.\\
That book has an unreadable font.\\
That book has lots of smudged type.\\
That book is covered with coffee.
\end{ex}
There seems to be a cline here from properties which are clearly true
of the content, through those which may be true only of a particular
edition or printing through to those which are true only of a copy 
(cf.~Cruse 1986:71).
Co-predication of the first and last properties seems
odd, as in \exnum{+1}{}.
\begin{ex}
? That book is full of metaphorical language
and is covered with coffee, so it's very hard to read.
\end{ex}
But co-predication of adjacent pairs seems natural in all cases, for
example \exnum{+1}{}
\begin{ex}
That book is full of typographic errors and has an unreadable font. 
\end{ex}

If we treat these senses as cases of constructional polysemy,
co-predication is predicted.  Thus {\it book} can have a formal role
and a content role in its qualia structure.  On this basis, there is
no necessary conflict between properties such as {\it is full of long
sentences} and {\it has coffee spilt on it}.  This treatment will not,
therefore, account for the apparent oddity of some co-predications.
However, although it 
is standardly assumed that cases of zeugma provide evidence for lexical
ambiguity, it is not clear that this is justifiable.  
Although we must assume, within a unification based account, that acceptable
co-predications imply the existence of a single structure, it does not
follow that the converse is true.
As we suggested above, oddness of co-predication can be simply due to
incompatability of the predicates.  Furthermore, there is clear evidence
that some sort of pragmatic principle of cohesion must be postulated to
account for the unacceptability of some readings where lexical ambiguity
cannot be involved.  For example, \exnum{+1}{}
has readings where the gardener bought either fruit or trees, 
but does not have the crossed interpretations where apple tree and pear
fruits were purchased or vice versa.  
\begin{ex}
The gardener bought three apples and two pears.
\end{ex}
Coherence also means that repeated uses of the same homonymous form will
tend to have the same interpretation, as in \exnum{+1}{}, where the crossed
interpretation, although possible, is dispreferred (see e.g. van Deemter,
1990).
\begin{ex}
John gave four files to Mary and three files to Sue.
\end{ex}
Assuming that some such principle is involved, it would also account
for the oddness of cases such as {\it fast and bearded typist}, {\it
tasty and skinny chicken} where we are predicating properties of
distinct aspects of the entity, without there being any apparent
connection between these aspects.  The acceptable examples, such as
{\it fast and intelligent typist}, {\it tasty and corn-fed chicken},
are those where the distinct aspects are nevertheless related --- good
typists might be expected to be both fast and intelligent, the food a
chicken is given is known to affect the flavour of its meat, and so on
(see above).  Given this, it is tempting to assume a single structure
for {\it book}.

However, other examples show even more complex polysemy: {\it
newspaper} can also refer to the physical copy or the abstract text
(of a particular issue), equivalent sentences to those above can be
constructed and the same remarks apply to these as to {\it
book}.  But {\it newspaper} can also refer to an abstract entity other
than the text.  This is somewhat hard to categorise --- it is not
necessarily a company, as ownership and editors can change without there
being a different newspaper and so on.  It seems plausible to suggest
that newspapers are regarded as (named) institutions in themselves.
Whatever their ontological status, it is clear that in some sentences
there is a notion of a `newspaper-as-institution', but it is not clear
that we can make a sharp distinction between this, the content of the
newspaper over a number of issues, and the abstract text reading \exnum{+1}{}.
\begin{ex}
That newspaper is owned by a trust.\\
That newspaper is left of centre.\\
That newspaper supported the Labour Party at the last election.\\
That newspaper carries long articles about the internal struggles of the
Labour Party.\\
That newspaper has obscure editorials.\\
That newspaper is full of metaphorical language.\\
That newspaper is full of long sentences.\\
That newspaper is full of spelling mistakes.\\
That newspaper is full of typographic errors.\\
That newspaper has an unreadable font.\\
That newspaper has lots of smudged type.\\
That newspaper is covered with coffee.
\end{ex}
Now again, the properties seem compatible with their neighbours, but
co-predication of the the first and last is odd, as in \exnum{+1}{}.
\begin{ex}
* That newspaper is owned by a trust and is covered with coffee.
\end{ex}
But in some cases co-predication of the copy sense and the
organisation sense does seem possible, as in \exnum{+1}{} (suggested to us by Geoff
Nunberg):
\begin{ex} 
The newspaper has been attacked by the opposition and publicly burned
by demonstrators.
\end{ex}

Despite this, assuming that a single structure can cover all the senses of {\it
newspaper} is highly problematic.  Constructing a qualia
structure to cover all the senses of {\it newspaper}
in such a way that different predicates
can apply appropriately is difficult, since it seems that the copy and
the organisation sense (at least) should have their own distinct qualia.  
It is also not clear that one sense can be regarded as primary.
Perhaps the most important point is that we
can quantify {\it newspaper} in either the copy or the organisation
sense and 
vagueness of interpretation with respect to the quantification
is not possible in such contexts.
Thus \exnum{+1}{}
has the interpretation that three newspapers-as-organisations have been
attacked, and some arbitrary number of copies pertaining to each have been
burned.  
\begin{ex} 
Three newspapers have been attacked by the opposition and publicly burned
by demonstrators.
\end{ex}

However, there is no reason within our account why both 
ambiguity/sense extension and vagueness/constructional
polysemy should not be involved, and this would account for
the data.
Thus for {\it newspaper}, we assume two structures, one corresponding
primarily to
the copy and one to the institution.  
Both of these may be involved in constructional polysemy --- the text and parent
organisation of the newspaper copy is accessible via its qualia, and
conversely the copies are accessible from the structure representing the
parent organisation.
Note that no intermediate primary structure
corresponding to one edition of a newspaper seems to be justified --- {\it
three newspapers} cannot mean three editions of the same paper, considered
as abstract texts, for
example.  
Thus, in this case, the abstract contents of the physical object 
can only be accessed indirectly.

Thus the account we have developed here is able to capture facts of
co-predication in coordinate structures with constructional polysemy
and sense extension insofar as the latter is acceptable. In addition,
our account makes further predictions regarding the grammaticality of
non-constituent coordination in cases of constructional polysemy. We
have not considered the interaction of lexical rules of sense
extension with indexical and anaphoric pronouns (see Nunberg,
1993). It is clear that there are many challenges to be faced here,
and the consequent complication of the theory of anaphora must be
weighed against the advantages gained here in the succinct
characterisation of the behaviour of verbs, such as {\it enjoy}, which
subcategorise for multiple complementation within the same or highly
related senses, and in the capturing of similarities between sense
extension and other lexical processes.

\section{The semi-productivity of lexical rules}

There are several empirical problems with the account of lexical rules
we have developed. Some of these problems are shared with other
generative accounts of morphological operations (see e.g.~Bauer, 1983
for extensive discussion), others are more specific to our proposal to
account for sense extensions in the same fashion. It is well known
that morphological processes tend to be semi-productive and are rarely
(if ever) exceptionless (e.g. Bolinger, 1975; Aronoff, 1976); for
instance, the rule of {\it -er} nominalisation in English creates
deverbal nouns which denote the subject of the underlying predicate --
typically an agent, as in {\it teacher} or {\it thinker}, sometimes an
instrument, as in {\it (dish)washer} or {\it (bottle) opener} where
the instrumental argument can occur as subject, and occasionally the
patient {\it sticker} or {\it (best)seller}. However, this rule is not
fully productive because items such as {\it banker} and {\it
stationer} do not have the predicted meaning, whilst a form like {\it
stealer} is blocked by {\it thief}, though is more acceptable when its
meaning is specialised (and made non-synonymous) with a postmodifier
-- {\it stealer of fast sports cars / hearts}. Rappaport and Levin
(1990) argue that both the agent, instrument and patient versions of
{\it -er} suffixation are rule-governed and the verbs which undergo
the latter are at least partly predictable on the basis that they
allow middle formation and thus the promotion to subject of the
patient argument -- {\it The book sold well}. If we assume that
subregularities block regularities and exceptions block all
regularities, we can account for this pattern of data without problem.
The mechanism required to achieve this looks very similar to that
which is required to block {\it pig} having a meat reading in normal
circumstances (Briscoe \etal., 1994).

Lexical rules of sense extension, as we have described them, clearly
lead to overgeneration.  For example, given the sense extension rules
for grinding, portioning and animal-metaphor discussed above,
\exnum{+1}{a} has the interpretations \exnum{+1}{b},\exnum{+1}{c},
\exnum{+1}{d} and \exnum{+1}{e}:
\begin{ex}
\begin{subex}
John saw some lambs.
\end{subex}
\begin{subex}
John saw some animals.
\end{subex}
\begin{subex}
John saw some humans with some lamb-like properties.
\end{subex}
\begin{subex}
John saw some portions of lamb meat.
\end{subex}
\begin{subex}
John saw some portions of substance derived from humans with some 
lamb-like properties.
\end{subex}
\end{ex}
This problem of rules of sense extension feeding further rules is
exacerbated by the lack of morphological marking of the change; that
is, the fact that these are rules of conversion rather than
derivation. Similar problems arise with uncontroversially
`morphological' conversion and derivation; for example, a generative
rule-governed approach would have problems explaining why forms such
as {\it unreuntie} are not attested. In the literature on lexical
rules, this has led to vacillation between interpretations of lexical
rules as `redundancy' statements relating pre-existent entries
(e.g.~Jackendoff, 1975) and as fully productive generative devices
creating new entries from existing ones which match their structural
description (e.g.~Pollard and Sag, 1987). Neither approach is fully
satisfactory since the former fails to capture the semi-productive
nature of these rules and the latter leads to overgeneration.

Finally, it is clear that in the case of a sense extension such as
grinding, there is distinct variability in the application of the rule
to lexical items even within a conventionalised subcase, such as meat
grinding; thus, {\it lamb}, {\it chicken} and {\it haddock} are common
and established, whilst {\it mole} and {\it alligator tail} are
not. It is also clear that language users are sensitive to such
frequency-based judgements concerning the relative novelty of
usages. The same issue arises with derivational morphology in that
many forms which are predicted by productive derivational rules are
not attested, for example, {\it hammerer} and {\it nailer} can be
formed by applying {\it er} nominalisation to the `incorporated' verbs
{\it hammer} and {\it nail}, respectively. However, English speakers
are liable to react to these forms in much the same way they would
react to {\it mole} in the meat sense: with a degree of resistance,
but without serious difficulty in interpretation. Bauer (1983:71f), in
supporting the view that lexical rules should be treated as fully
productive generative rules analogous to those employed in syntactic
description, argues that it is this greater `item-familiarity' of
lexical items which allows judgements of relative novelty /
conventionality to be built up. He points out that there are simply
too many combinatoric possibilities at the sentential level for the
frequency of particular combinations to be assessed with any
confidence by a language user. However, in the case of words and, we
might add, idioms the range of possibilities though large is not so
great that judgements of novelty based on frequency of use cannot be
acquired. 
Bauer argues, therefore, that accounting for
semi-productivity is an issue of performance, not competence.

The frequency with which a given word form is associated with a
particular sense (or lexical entry) is often highly skewed; Church
(1988) points out that a model of part-of-speech assignment in context
will be 90\% accurate (for English) if it simply chooses the lexically
most frequent part-of-speech for a given word. The incidence of senses
of words may well turn out to be similarly skewed. In the absence of
other factors, it seems very likely that language users utilise
frequency information to resolve indeterminacies in both generation
and interpretation. Such a strategy is compatible with and may well
underlie the Gricean Maxim of Manner, in that ambiguities in language
will be more easily interpretable if there is a tacit agreement not to
utilise abnormal or rare means of conveying particular messages. We
can model this aspect of language use as a conditional probability
that a word form will be used in a specific sense; that is, is associated
with a specific entry 
($Pr(\mbox{\it lexical-entry}\,|\,\mbox{\it word-form})$). We assume
that such probabilities are acquired for both basic and derived senses
(lexical entries) independently of the lexical rules used to create
derived senses. Thus we make no claim that a derived sense will
necessarily be less frequent than a basic one; in the case of a word
such as {\it turkey} in English our intuition is that the ground or
animal-metaphor senses are more frequent than the basic sense.  It
might seem that this assumption commits us to a `fully entry' theory
of the lexicon (e.g.~Aronoff, 1976) in which all possible words are
present; that is, the consequences of lexical rules are
precomputed. In the limit, the full entry theory cannot be correct
because of the presence of recursive derivational rules such as {\it
re-}, {\it anti-} or {\it great-} prefixation in words such as {\it
rereprogram}, {\it anti-anti-missile} or {\it
great-great-grandfather}, and in our theory of `cyclic' rules of sense
extension such as portioning and grinding.  Instead we adopt an
intermediate position in which we claim that basic entries are
augmented with a representation of the attested lexical rules which
have applied to them and any such derived chains, where both the basic
entry and these `abbreviated' derived entries are associated with a
probability.\footnote{Modulo the probabilistic interpretation, this
manner of encoding the (non-)application of a lexical rule has been
deployed in many theories; e.g.~Flickinger and Nerbonne (1992) and
Sanfilippo (1993) in recent accounts of verbal diathesis alternations.}
For example, a word form such as {\it rabbit} might be associated with
a basic entry like that illustrated in Figure~\ref{rabbit}, in which
meat grinding is shown to be (hypothetically) more probable than
grinding, meat grinding and portioning, or fur/skin
grinding. Following Cruse (1986) we might refer to this as the lexeme
for {\it rabbit}, in the sense that this basic entry encapsulates our
knowledge of the (predictable) behaviour of this word-form (though not
of its morphological derivatives, such as {\it rabbit-like}, and so
forth).
\begin{figure}
{\centering
\tiny
$\avmplus{\att{lex-count-noun}\\
         \attvaltyp{ORTH}{rabbit}\\
         \attvalshrunktyp{CAT}{noun-cat}\\
         \attvalshrunktyp{SEM}{obj-noun-formula}\\
         \attvaltyp{PROB}{0.4}\\
         \attvaltyp{LRS}{grinding(0.05), meat-grdg(0.3),
meat-grdg+portioning(0.15), fur/skin-grdg(0.1)}
}$

}
\caption{Lexeme for {\it rabbit}}
\label{rabbit}
\end{figure}
The attribute {\sc lrs} associated with the lexeme for {\it rabbit}
records which combinations of lexical rules have been attested with what
frequency in the experience of the language user.\footnote{It is
plausible to imagine that language users are able to memorise some
estimate of the relative frequency with which a word form and sense
occur, though it is unlikely that this process is accurate enough to
derive probabilities. Nevertheless, probability theory offers a
precise and well-understood theory within which such intuitions can be
formalised.} If we assume that speakers choose well-attested
high-frequency forms to realise particular senses and listeners choose
well-attested high-frequency senses when faced with ambiguity, then
much of the `semi-productivity' of lexical rules can be treated as a
side-effect of performance. For instance, we would predict that in the
`null' or a neutral context \exnum{+1}{a} will be interpreted as
rabbit meat, and \exnum{+1}{b} will be interpreted as animals.
\begin{ex}
\begin{subex}
John prefers rabbit
\end{subex}
\begin{subex}
John wants three rabbits
\end{subex}
\begin{subex}
The diners ordered three rabbits
\end{subex}
\end{ex}
On the other hand, less frequent but attested senses should be chosen
when other contextual factors so dictate, as in
\exnum{0}{c}.   
In order to specify precisely how this
interpretation is preferred, and to formalise the notion of neutral context
within this framework, we would need to develop either a
thorough-going account of the interaction of lexical probabilities
with probabilities associated with specific sentential
interpretations, or an account of how probabilities reflecting
frequency of usage interact with pragmatic principles establishing
discourse coherence (or both). This would take us well beyond the
scope of this paper, but see e.g.~Wu (1990), Lascarides \etal.,
(forthcoming).

In addition to such lexical probabilities, we also think that
probability may play a role in the application of lexical rules in
novel usage. Under the current proposal, lexical rules will have
something akin to the status of `redundancy' rules in that they can be
used to create appropriate lexical entries on demand for attested
senses of a word form; that is, those which have a non-zero
probability in the associated lexeme entry. However, in the situation
where an interpretation for a novel usage is called for, an assessment
of the relative probability of extant lexical rules would provide a
means for adopting the most likely `analogous' interpretation. For
instance, interpreting examples such as \exnum{+1}{}, the listener who
had not experienced examples of any variant of grinding with these
nouns might choose the rule with the highest probability given the
semantic type of the noun.
\begin{ex}
\begin{subex}
John prefers alligator tail / mole 
\end{subex}
\begin{subex}
John prefers chinchilla
\end{subex}
\begin{subex}
John prefers pig
\end{subex}
\end{ex}
The probability of a lexical rule might be derived by comparing the
number of lexemes to which the rule could apply (i.e.~that it unifies
with) where that sense is unattested, to those for which it is
attested.  Since grinding can apply to any count noun but will be
attested for very few, whilst meat grinding can only apply to animal
denoting nouns and will be attested for a higher proportion, this
predicts that \exnum{0}{a} will be interpreted as cases of meat
grinding even in a neutral context. Thus, we can account for
productive or `analogical' use of a lexical rule to interpret a novel
usage.\footnote{Note that this account has little to say about the
conditions under which novel uses will be created, so we will need a
further pragmatic theory of the factors licensing novel usage and of
the possibility of such usage becoming conventionalised (see
e.g.~Bauer, 1983). It might be possible to account for the acquisition
of lexical rules in terms of a {\it post hoc} process of
generalisation between `basic' and `derived' entries at some point
when the productivity of the putative rule reached some probabilistic
threshold.}  Assuming that the rule of fur/skin grinding is restricted
to words denoting animals with fur or `good' skin we may be able to
construct a similar account for the preferred interpretation of
\exnum{0}{b}.  However, the notion of semantic type may need to be
more fine-grained than is plausible or desirable in a lexicon if we
are to account for all such preferences in this manner, since
\exnum{0}{b} shows a preference for fur/skin grinding probably as a
result of the salience of fur in distinguishing chinchillas from other
types of rodent, rabbit or cat.  Nevertheless, however this is
achieved, it is ultimately a fact about the word and associated sense(s)
rather than a fact about animals, since it is irrelevant whether, in
reality, more chinchilla animals are worn than eaten. The case of
\exnum{0}{c} is different though, since this approach would predict a
meat reading on the basis of the greater probability of meat grinding
than grinding. However, the preferred interpretation is probably the
less specific `pig-stuff' in a neutral context, because of the
blocking of this sense by {\it pork}.

Thus the generation and interpretation of normally blocked forms
(unblocking) seems to require a different type of explanation.
Briscoe \etal. (1994) proposed to account for cases of preemption or
blocking by introducing a defeasible notion of lexical rule and
allowing the output of such rules to be defeasibly overridden in the
case where there was preemption by synonymy or by phonological
form. The (pragmatic) principle of blocking introduced case specific
defeasible blocking statements that could be themselves overridden in
pragmatically marked contexts to account for the occasional usages of,
for example, {\it pig} to mean meat with additional affect, and so
forth. In this manner, the approach captured Bauer's (1983:87) insight
that blocking is a bar to the institutionalisation (in our terms
conventionalisation) of a meaning rather than an outright ban on its
use. In this paper, we have presented a rather different formalisation
of lexical rules in which the output of the rule itself is not
defeasible.  From our current perspective, preemption by synonymy can
be explained simply by assuming that speakers will use higher
frequency forms to convey a given meaning.  Thus an extended meaning
will not become conventionalised if a common synonym exists.  This
does not, however, explain the exceptions where blocked forms do occur
(except those where the speaker or hearer are unaware of the synonym)
nor the effects of their use.  The biggest challenge to our current
proposal will be to develop an account of the interaction of
frequency-based judgements represented as probabilities with default
constraints, such as those which allow unblocking.  From the
perspective of natural language processing a viable alternative might
be to model all such pragmatic phenomena probabilistically, perhaps
deriving data on the frequency of predicted senses from large corpora
(e.g.  Pustejovsky \etal., 1993). However, if we wish to limit the role
of probabilities to modelling the frequency-based aspects of
semi-productivity and develop theoretical accounts of blocking and
unblocking and, say, the interaction of frequency-based judgements
with contextual factors favouring a low probability sense, then it
will be necessary to utilise a non-monotonic logic in which it is
possible to reason about probabilities (see e.g.~Pearl, 1988).

\section{Conclusion}

We have drawn a distinction between some cases of sense modulation and
change which we have termed constructional polysemy and sense
extension, respectively. This distinction is based on behaviour under
co-predication and the traditional distinction between vagueness and
ambiguity. We also pointed out in \S5.2 that in the absence of clear
tests, some cases remain difficult to classify with respect to this
distinction.

Both constructional polysemy and sense extension are productive
processes which require `generative' lexical mechanisms, in the sense
of Pustejovsky (1991). We have proposed to account for some cases of
constructional polysemy utilising the notion of nominal qualia
structure and predicate coercion. We have formalised this account in a
constraint based approach to linguistic description which has been
implemented -- the LRL/LKB (Copestake, 1992, 1993b). We have argued that
this approach, unlike those of Briscoe \etal. (1990) and Pustejovsky
(1993), is capable of capturing many facts of
`co-predication'. However, our account requires extension in order to
deal with the cases of non-constituent coordination discussed in \S5.1,
in line with other constraint based approaches to coordination
(e.g. Shieber, 1992). Furthermore, it needs to be
supplemented with a pragmatic account of cohesive co-predication
along the lines of Nunberg (this volume), as discussed in \S5.

We have argued that sense extensions are semi-productive related sense
changes: we cannot simply list all the extended senses in the lexicon,
since new `analogous' cases which will not be listed occur. In
addition, there are cross-linguistic exceptions and differences of
encoding, conventionalised subcases and so forth, which all suggest a
sign based, lexical rule account. Nevertheless, sense extensions like
other lexical rules of conversion and derivation can be blocked and
are applied conservatively. We outlined in \S6 an account of the
semi-productivity of lexical rules in terms of a probabilistic
performance account of their deployment in language production and
interpretation. We have also suggested that this account should be
integrated with an independent account of blocking or preemption
(Briscoe \etal., 1994), but this integration remains to be undertaken.

The LRL/LKB framework has also been used to represent cross-linguistic
lexical translation (non-)equivalence (Copestake and Sanfilippo,
1993), verbal diathesis alternations (Sanfilippo, 1993) and as a target
representational framework for the semi-automatic acquisition of
lexical entries from machine-readable dictionaries (see papers in
Briscoe \etal., 1993 and references therein). In future work, we intend
to extend the framework to deal more adequately with default aspects
of lexical behaviour and with the integration of lexical and pragmatic
phenomena.

{\small
\section*{References}
% first argument - i.e. #1 is always author
% #2 is title
% last is date
% agreed author format is, for example
% Alshawi, H., D. Carter, M. Rayner and B. Gamb\"ack
% 
% the only formatting commands that should appear in fields
% are those to mark idiosyncratic information like accents
\newcommand{\book}[4]{\item #1 (#4) {\it #2,} #3.}
% #3 is publisher
\newcommand{\unpub}[4]{\item #1 (#4) `#2', #3.}
% for tech reports etc
% #3 is information about institution etc
\newcommand{\bookart}[7]{\item #1 (#7) `#2' in #5 (ed.), {\it #4,} #6, pp.~#3.}
% published book article (old \barticle)
% #3 is page numbers 
% #4 book title
% #5 editors
% #6 publishers
\newcommand{\bookartnoed}[6]{\item #1 (#6) `#2' in {\it #4,} #5, pp.~#3.}
% book article where editors are unknown
% #3 is page numbers 
% #4 book title
% #5 publishers
\newcommand{\bookartnopp}[6]{\item #1 (#6) `#2' in #4 (ed.), {\it
#3,} #5.}
% book article where page numbers are unknown
% #3 book title
% #4 editors
% #5 publishers
\newcommand{\forthart}[6]{\item #1 (#6, forthcoming) `#2' in #4 (ed.), {\it #3,} #5.}
% article in forthcoming book (old \farticle}
% #3 book title
% #4 editors
% #5 publishers
\newcommand{\journart}[6]{\item #1 (#6) `#2', {\it #3,} {\bf #4},
#5.}
% article in journal (old \jarticle)
% #3 name of journal
% #4 volume
% #5 pages
\newcommand{\journartnopp}[5]{\item #1 (#5) `#2', {\it #3,} 
{\bf #4}.}
% article in journal no page numbers
% #3 name of journal
% #4 volume
\newcommand{\procart}[6]{\item #1 (#6) `#2', {\it Proceedings of the
#3,} #4, pp.~#5.}
% article in proceedings (old \particle)
% #3 name of conference
% #4 venue
% #5 pages
\newcommand{\pubprocart}[7]{\item #1 (#7) `#2', {\it Proceedings of the
#3,} #4, ,#5, pp.~#6.}
% #3 name of conference
% #4 venue
% #5 publishers
% #6 pages
\newcommand{\procartnopp}[5]{\item #1 (#5) `#2', {\it Proceedings of the
#3,} #4.}
% article in proceedings without known page numbers
% #3 name of conference
% #4 venue
\newcommand{\pubprocartnopp}[6]{\item #1 (#6) `#2', {\it Proceedings of the
#3,} #4, #5.}
% article in proceedings without known page numbers
% #3 name of conference
% #4 venue
% #5 publishers
\newcommand{\procartnoppnoplace}[4]{\item #1 (#4) `#2', {\it Proceedings of the
#3}.}
% article in proceedings without known page numbers without place
% where meeting happened
% #3 name of conference
\newcommand{\procartnoplace}[5]{\item #1 (#5) `#2', {\it Proceedings of the
#3,} pp.~#4.}
% article in proceedings where the venue is not known
% #3 name of conference
% #4 pages
%\newcommand{\acqwp}{ESPRIT BRA-3030 ACQUILEX WP NO.}
%\newcommand{\aunpub}[5]{\item #1 (#4) {\it #2.}\\ \acqwp #3}


\begin{list}{}
   {\leftmargin 1.6em
    \itemindent -\leftmargin
    \itemsep 0pt plus 1pt
    \parsep 0pt plus 1pt}

\book{Alshawi, H. (ed.)}
     {The Core Language Engine}
     {MIT Press, Cambridge, Mass}
     {1992}


\book{Apresjan, Ju D.}
    {Regular Polysemy}
    {Mouton, The Hague, The Netherlands}
    {1973}


\book{Aronoff, M.}
     {Word Formation in Generative Grammar} 
     {Linguistic Inquiry Monograph 1. MIT Press, Cambridge, Mass}
     {1976}

%
\unpub{Atkins, B.T.}
     {Lexical Rules: a starter pack}
     {Ms.~Oxford University Press}
     {1990}

%
\bookartnopp{Atkins, B.T. and B.~Levin} 
         {Admitting Impediments}
         {Lexical Acquisition: Using On-Line Resources to Build a Lexicon}
         {U.~Zernik}
         {Lawrence Erlbaum, New Jersey}
         {1992}

%   (e.g.~Baker, 1988)?? Incorporation, MIT Press,
\book{Baker, M.C.}
     {Incorporation: a theory of grammatical function changing}
     {University of Chicago Press, Chicago}
     {1988}

%
\book{Bauer, L.}
     {English word-formation}
     {Cambridge University Press, Cambridge, England}
     {1983}

\journart{Bierwisch, M.}
         {Formal and lexical semantics}
         {Linguistische Berichte}  
         {80} 
         {3--17}
         {1982}

\book{Bolinger, D. L.} 
{Aspects of Language}
{Harcourt, Brace and Jovanovich: New York}
{1975}

%
\procart{Briscoe, E. J., A.~Copestake  and B.~Boguraev}
    {Enjoy the paper: lexical semantics via lexicology}
    {13th International Conference on Computational Linguistics (COLING-90)}
    {Helsinki}
    {42--47}
    {1990}

%
\procart{Briscoe, E. J., and A. Copestake }
{Sense extensions as lexical rules}
{IJCAI Workshop on
Computational Approaches to Non-Literal Language}
{Sydney, Australia} 
{12--20}
{1991}

%
\book{Briscoe, E. J., A. Copestake and V. de Paiva (eds)}
{Inheritance, defaults and the lexicon}
{Cambridge University Press, Cambridge, England}
{1993}

%Briscoe \etal., 1994
\bookartnopp{Briscoe, E.J., A.~Copestake and A.~Lascarides}
            {Blocking}
            {Computational Lexical Semantics}
            {P.~St.~Dizier and E.~Viegas}            
            {Cambridge University Press}
            {1994, in press}

%
\book{Carpenter, R.}
{The logic of typed feature structures}
{Cambridge University Press, Cambridge, England} 
{1992}

%   Church 1988 ? PARTS tagging
\procart{Church, K.}
{A stochastic parts program and noun phrase parser for unrestricted text}
{Second Conference on Applied Natural Language Processing (ANLP-88)}
{Austin, Texas}
{136--143}
{1988}


\journart{Clark, E. V. and H. H. Clark}
     {When nouns surface as verbs}
     {Language}
     {55}
     {767--811}
     {1979}


%Cooper, 1991
\procart{Cooper, R.P.}
      {Coordination in Unification-Based Grammars}
      {5th Conference of the European Chapter of the Association 
for Computational Linguistics (EACL-91)}
      {Berlin}
      {167--172}
      {1991}

\unpub{Copestake, A.}
{The representation of lexical semantic information}
{Doctoral dissertation, University of Sussex,
Cognitive Science Research Paper CSRP 280}
{1992}


\bookart{Copestake, A.}
{Defaults in Lexical Representation}
{223--245}
{Inheritance, Defaults and the Lexicon}
{Briscoe, E.J., A.~Copestake and V.~de Paiva}
{Cambridge University Press}
{1993a}

\unpub{Copestake, A.}
     {The Compleat LKB}
     {ACQUILEX-II Deliverable, 3.1}
     {1993b}

%
\bookart{Copestake, A. and E.~J.~Briscoe}
     {Lexical operations in a unification based framework}
     {101--119}
     {Lexical Semantics and Knowledge
     Representation.  Proceedings of the first SIGLEX Workshop, 
     Berkeley, CA}
     {J. Pustejovsky and S. Bergler}
     {Springer-Verlag, Berlin}
     {1992}

%Copestake and Sanfilippo (1993)
\procartnopp{Copestake, A. and A.~Sanfilippo}
{Multilingual lexical representation} 
{AAAI Spring Symposium on Building Lexicons for Machine Translation}
{Stanford, CA} 
{1993}


%
\book{Cruse,~D.~A.}
     {Lexical semantics}
     {Cambridge University Press, Cambridge, England}
     {1986}

%van Deemter, 1990)
% OTS-WP-CL-91-001
\procart{van Deemter, K.}
     {The ambiguous logic of Ambiguity}
     {First CLIN Meeting}
     {Utrecht, The Netherlands}
     {17--32}
     {1990}

\book{Fauconnier, G.}
    {Mental spaces: aspects of meaning construction in natural language}
    {MIT Press, Cambridge, Mass.}
    {1985}

%   Flickinger and Nerbonne (1992 - CL paper? yes
\journart{Flickinger, D. and J.~Nerbonne}
{Inheritance and complementation: A case study of {\it easy}
adjectives and related nouns}
         {Computational Linguistics}
         {18.3}
         {269--310}
         {1992}


\procart{Godard, D. and J.~Jayez}
        {Towards a proper treatment of coercion phenomena}
        {Sixth Conference of the European Chapter of the Association for
Computational Linguistics (EACL-93)}
        {Utrecht, The Netherlands}
        {168--177}
        {1993}

%Hale, K & Keyser, S.J. (eds.) The View from Building 20, MIT Press,
%1993, Lexical Incorporation
\bookart{Hale, K. and S. J. Keyser}
       {On argument structure and the lexical expression of syntactic
relations}
       {53--110}
       {The View from Building 20: Essays in Honor of Sylvain Bromberger}
       {Hale, K. and S. J. Keyser}
       {MIT Press, Cambridge, Mass}
       {1993}

%    (e.g.~Hobbs \etal., 1990 ?? SRI TR on Tacitus
\unpub{Hobbs, J.R., M.~Stickel, D.~Appelt and P.~Martin}
   {Interpretation as Abduction}
   {Technical Note No.~499, Artificial Intelligence Centre, SRI
International, Menlo Park, CA}
   {1990}

%   (e.g.~Jackendoff, 1975) ? Morph & semantic regs in the lexicon Lg
% 51, 3 639-71.
\journart{Jackendoff,  R.}
    {Morphological and semantic regularities in the lexicon}
    {Language}
    {51(3)}
    {639--71}
    {1975}
    

%Krieger and Nerbonne (1993)
\bookart{Krieger, H-U. and J.~Nerbonne}
    {Feature-based inheritance networks for computational lexicons}
    {90--137}
    {Inheritance, defaults and the lexicon}
    {E.~J.~Briscoe, A.~Copestake and V.~de~Paiva}
    {Cambridge University Press, Cambridge, England}
    {1993}

\procart{Krifka, M.}
{Nominal reference and temporal constitution: towards a semantics of quantity}
    {6th Amsterdam Colloquium}
    {University of Amsterdam}
    {153--173}
    {1987}

%   (e.g.~Lakoff, 1987) 
\book{Lakoff, G.}
     {Women, fire, and dangerous things: what categories reveal about the mind}
     {University of Chicago Press, Chicago}
     {1987}


%
\book{Lakoff, G. and M.~Johnson}
     {Metaphors we live by}
     {University of Chicago Press, Chicago}
     {1980}

%   Lascarides etal (forthcoming) 
\unpub{Lascarides, A., E.J.~Briscoe, N.~Asher and A.~Copestake}
      {Persistent associative default unification}
      {ACQUILEX Working Paper}
      {forthcoming}

%
\book{Levin,  B.}
{Towards a lexical organization of English verbs}
{Chicago University Press, Chicago}
{1993}

% Link 1983
\bookart{Link, G.}
    {The logical analysis of plurals and mass terms: a lattice-theoretical
approach}
    {302--323}
    {Meaning, use and interpretation of language}
    {B\"{a}uerle, Schwarze and von Stechow}
    {de Gruyter, Berlin}
    {1983}


% Martin, 1990 
\book{Martin, J.}
     {A Computational Model of Metaphor Interpretation}
     {Academic Press, Cambridge, Mass}
     {1990}

%
\unpub{Nunberg, G. D.}
{The pragmatics of reference}
{Doctoral Dissertation, CUNY Graduate Center, reproduced by the
Indiana University Linguistics Club}
{1978}

%   Nunberg 1979 - paper ? yes
\journart{Nunberg, G. D.}
{The non-uniqueness of semantic solutions: polysemy}
{Linguistics and Philosophy}
{3}
{145--184}
{1979}

% Nunberg 1991 ? On the meaning and interp of indexical exprs. L&P
\journart{Nunberg, G.D.}
{On the meaning and interpretation of indexical expressions}
{Linguistics and Philosophy}
{16}
{1--43}
{1993}


%
\unpub{Nunberg, G.D. and A. Zaenen}
      {Systematic polysemy in lexicology and lexicography}
      {Proceedings of Euralex92, Tampere, Finland}
      {1992}

\book{Ojeda, A.}
     {Linguistic Individuals}
     {CSLI Lecture notes 31.  CSLI and University of Chicago Press}
     {1993}
     

%
\bookart{Ostler, N. and B.T. Atkins}
     {Predictable meaning shift: some linguistic properties of lexical
implication rules}
     {87--100}
     {Lexical Semantics and Knowledge
     Representation.  Proceedings of the first SIGLEX Workshop, 
     Berkeley, CA}
     {J. Pustejovsky and S. Bergler}
     {Springer-Verlag, Berlin}
     {1992}

%   Partee 1992 ?? Fml and Comp Sems. (eds) Johnson, R etc 
\bookart{Partee, B.}
   {Syntactic categories and semantic type}
   {97--126}
   {Computional linguistics and formal semantics}
   {M.~Rosner and R.~Johnson}
   {Cambridge University Press, Cambridge, England}
   {1992}


%   Pearl, 1988 Prob reasoning in intell systems, Morgan Kaufmann
\book{Pearl, J.}
     {Probabilistic reasoning in intelligent systems}
     {Morgan Kaufmann}
     {1988}


% Pelletier and Schubert 1989
\bookart{Pelletier, F. J., and L. K. Schubert} 
    {Mass expressions}
    {327--407}
    {Handbook of philosophical logic, Vol.~IV: Topics in the Philosophy of Language}
    {D.~Gabbay and F.~Guenthner}
    {Reidel, Dordrecht}
    {1989}

\bookart{Pelletier, F.J., and L. K. Schubert}
    {Problems in the representation of the logical form of 
generics, plurals, and mass nouns}
    {385--451}
    {New directions in semantics}
    {LePore}  
    {Academic Press, London}
    {1988}

\book{Pollard,  C. and I. Sag}
 {An information-based approach to syntax and semantics: 
Volume~1 fundamentals} 
 {CSLI Lecture Notes 13, Stanford CA}
 {1987}

%
\book{Pollard, C. and I. Sag}
    {Head-driven phrase structure grammar}
    {Chicago University Press, Chicago}
    {in press}

%
\journart{Pustejovsky, J.}
    {The generative lexicon}
    {Computational Linguistics}
    {17(4)}
    {409--441}
    {1991}


%   Pustejovsky, 1993 ?? Type coercion and lexical selection pp 73-96
% Semantics & the Lexicon, Kluwer, Dordrecht (ed). JP
\bookart{Pustejovsky, J.}
   {Type coercion and lexical selection}
   {73--96}
   {Semantics and the Lexicon}
   {J.~Pustejovsky}
   {Kluwer, Dordrecht}
   {1993}


%Pustejovsky (1994)
\bookartnopp{Pustejovsky, J.}
   {Linguistic constraints on type coercion}
            {Computational Lexical Semantics}
            {P.~St.~Dizier and E.~Viegas}            
            {Cambridge University Press}
            {1994, in press}

\journart{Pustejovsky, J. and B.~Boguraev}
      {Lexical knowledge representation and natural language processing}
      {Artificial Intelligence}
      {63}
      {193--223}
      {1993}

\bookartnopp{Rappaport, M. and B. Levin}
{{\it -er} Nominals: Implications for the theory of argument
structure}
{Syntax and the Lexicon}
{E.~Wehrli and T.~Stowell}
{Syntax and Semantics 26, Academic Press, New York}
{1990}


\unpub{Riehemann, S.}
    {Word formation in lexical type hierarchies}
    {M.Phil thesis, University of T\"{u}bingen, Germany}
    {1993}

% Sag \etal. 1985
\journart{Sag, I., G.~Gazdar, T.~Wasow and S.~Weisler}
     {Coordination and how to distinguish categories}
     {Natural Language and Linguistic Theory}
     {3}
     {117--171}
     {1985}


%
\bookart{Sanfilippo, A.}
    {LKB encoding of lexical knowledge from machine-readable dictionaries}
    {190--222}
    {Inheritance, defaults and the lexicon}
    {E.~J.~Briscoe, A.~Copestake and V.~de~Paiva}
    {Cambridge University Press, Cambridge, England}
    {1993} 

%Shieber, 1992
\book{Shieber, S.~M.}
{Constraint-based grammar formalisms}
{MIT Press, Cambridge, Mass.}
{1992}

%(Soler and Marti, 1993)
\unpub{Soler, C. and M.A.~Marti}
      {Dealing with lexical mismatches}
      {ACQUILEX working paper no.~2.4}
      {1993}

%    Sweetser 19?? ? From Etymology to pragmatics, CUP, 1990
\book{Sweetser, E.}
    {From etymology to pragmatics}
    {Cambridge University Press, Cambridge, England}
    {1990}

%\journart{Weinreich, U.}
%    {Webster's Third: A critique of its semantics}
%    {International Journal of American Linguistics}
%    {30}
%    {405--409}
%    {1964} 

\procart{Wu, D.}
{Probabilistic unification-based integration of syntactic and semantic
preferences for nominal compounds}
{13th International Conference on Computational Linguistics (Coling90)}
{Helsinki}
{413--418}
{1990}

\procart{Young, M. and W.~Rounds}
        {A logical semantics for non-monotonic sorts}
        {31st Conference of the Association for Computational Linguistics (ACL-93)}
        {Columbus, Ohio}
        {209--215}
        {1993}

\end{list}
}
\end{document}
