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\begin{document}
\thispagestyle{empty}
\vspace*{2in}
\begin{center}
{\Large \bf The representation of group denoting
          nouns in a lexical knowledge base}\\
\smallskip
Ann Copestake\\
\smallskip
University of Cambridge Computer Laboratory\\
New Museums Site, Pembroke Street, Cambridge, CB2 3QG, UK\\
\smallskip
January 1992 (revised version December 1992)\\
\smallskip
To appear in: P.~St.~Dizier and E.~Viegas (editors)
{\it Computational Lexical Semantics}, Cambridge University Press
(in press)\\
\bigskip
Revised version of ESPRIT BRA-3030 ACQUILEX Working Paper No. 037
\end{center}
\newpage
\setcounter{page}{1}
\begin{center}
{\Large \bf The representation of group denoting nouns in a lexical 
knowledge base}\\
{\large Ann Copestake}
\end{center}

\section*{Abstract}

In this paper we consider the representation of group denoting 
nouns, and the relationship between groups and their individual 
members, within the general 
framework of a computational treatment of lexical semantics which uses 
a typed unification based formalism to create a highly structured lexicon.
We illustrate how such a representation 
can be created
(semi-)automatically using machine readable dictionaries as a data source. 

\section{Introduction}
\label{intro}

The work reported here is part of research 
on the ACQUILEX project\footnote{ACQUILEX:
`The Acquisition of Lexical Knowledge for
Natural Language Processing Systems': Esprit BRA-3030.
For an overview
of ACQUILEX as a whole see Briscoe (1991).} which is
aimed at
the eventual development of a theoretically-motivated, but comprehensive and
computationally tractable, multilingual lexical knowledge base (LKB)
usable for natural language processing, lexicography and 
other applications.
One of the goals of the ACQUILEX project
was to demonstrate the feasibility of building an LKB 
by acquiring a substantial
portion of the information semi-automatically from 
machine readable dictionaries (MRDs).  
We have paid particular 
attention to lexical semantic information.  Our work therefore 
attempts to integrate several strands of research:
\begin{itemize}
\item Linguistic theories of the lexicon and lexical semantics.  In this paper
we will concentrate on the lexical semantics of nominals where our treatment is
broadly
based on that of Pustejovsky (1991), and in particular on his concepts
of the {\em generative lexicon} and of {\em qualia structure}.
\item  Knowledge representation techniques.  The formal lexical representation
language (LRL) used in the ACQUILEX LKB system is based 
on typed features structures
similar to those of
Carpenter (1990, 1992), augmented with default inheritance and 
lexical rules.  Our lexicons can thus be highly structured, hierarchical and 
generative.
\item Lexicography and computational lexicography.  
The work reported here makes extensive use of the Longman Dictionary 
of Contemporary English (LDOCE; Procter, 1978).
MRDs do not just provide
data about individual lexical items; 
our theories of the lexicon have been developed and refined by 
considering the implicit organisation of dictionaries and the insights of 
lexicographers.  
\end{itemize}
In this paper we will show how these strands can be combined in 
developing an appropriate representation for group nouns 
in the LRL, and in extracting
the requisite information automatically from MRDs.

\subsection{Qualia structure}
\label{qualia}

Our treatment of the lexical
semantics of nominals is ultimately based on Pustejovsky's approach,
and, in particular, his description of {\em qualia structure}.
Pustejovsky (1991) describes 
the qualia structure of a lexical item as 
consisting of the following four roles: 
\begin{description}
\item[Constitutive Role] The relation between an object and its constituents
or proper parts.
\item[Formal Role] That which distinguishes the object within a larger
domain.
\item[Telic Role] Purpose and function of the object.
\item[Agentive Role] Factors involved in the origin or ``bringing about''
of an object.
\end{description}
Pustejovsky argues that, rather than assuming that nominals just
behave as passive objects when they combine with verbs, we should treat them
as being as active in the semantics as the verb itself is.  He refers to
this behaviour as {\em cocompositionality}. 
The cocompositional behaviour of a noun 
is determined by its qualia structure.

For example, many verbs such as {\it enjoy} which can take a VP complement,
can be described as selecting semantically
for an event.  
\begin{ex}
Mary enjoys playing the guitar.
\end{ex}
However {\it enjoy} can also take an NP complement, and 
in sentences such as \exnum{+1}{}
the complement {\it the book} apparently denotes an object.
\begin{ex}
Mary enjoyed the book.
\end{ex} 
Traditionally the only way to handle
this is to assume two lexical entries for {\it enjoy}
and to relate the different senses by meaning postulates.
However this is unsatisfactory since it leads to a proliferation of senses
in the lexicon and
it does not generalise to other cases
where a noun phrase is interpreted as an event, such as 
\exnum{+1}{}.
\begin{ex}
After three glasses of champagne, John felt much happier.
\end{ex}
Furthermore, examples such as \exnum{+1}{} seem perfectly acceptable:
\begin{ex}
Mary enjoys books, television and playing the guitar.
\end{ex}
However, under quite 
generally accepted assumptions about the nature of coordination
and lexical ambiguity (e.g. Zwicky and Sadock, 1975; Cruse, 1986),
only one sense of {\it enjoy} can be involved in \exnum{0}{}.

Pustejovsky proposes that examples such as \exnum{-2}{} be treated as
involving {\it logical metonymy}. 
The sentence is interpreted as:
\begin{ex}
Mary enjoyed some event associated with the book.
\end{ex}
The qualia structure for nouns specifies possible associated events.
In this case,
for example, the telic (purpose) role of the qualia structure for {\it book}
has a value equivalent to {\it reading}.  When combined
with {\it enjoy}, type coercion occurs, because {\it enjoy} selects
for an event rather than an object, and the particular sort of event
which is likely to be involved can be determined from the qualia
structure,
which results in a default
interpretation for \exnum{-3}{} equivalent to: 
\begin{ex}
Mary enjoyed reading the book.
\end{ex}

In a marked context the default interpretation might be overridden or blocked. 
For example, if
Mary was the name of a goat, it might be inferred that she enjoyed
eating the book rather than reading it; this 
is assumed to be part of pragmatics rather than lexical semantics.
In such cases the type coercion to an event
still occurs but the nature of the event is overridden.
In cases where the lexical semantics of the noun would not specify a telic
role, or where the event specified would
not be of an appropriate type, the corresponding sentences are odd:
\begin{ex}
? John enjoyed the rock.
\end{ex}
Since {\it rock} is not regarded as having a 
specified telic role, 
the type of event which results from the metonymic coercion process
is unknown, and the sentence seems bad.

For details of the way in which 
qualia structure and logical metonymy can be formally
represented using a computationally tractable language, see
Briscoe {\it et al.} (1990) and Copestake and Briscoe (1991).
In the remainder of this paper, we will describe our current lexical
representation language, and illustrate how we can use this
to represent group nouns, in a way which integrates with the earlier 
accounts.   
As in the earlier papers, we
concentrate on the issues of how the lexicon may be structured, in order to
provide an efficient representation
of lexical semantic information in the paradigmatic plane,
and on how
the description of lexical semantic structure may be
integrated with a compositional semantic account.
We conclude by describing how lexical information about group nouns
may be extracted automatically from dictionary definitions.

\section{The Lexical Representation Language}
\label{lrl}

Our lexical representation language (LRL) is unification-based, allowing
complex interconnections between syntactic and semantic information to
be defined, and making a tight interface possible between the lexicon
and other components of NLP systems, e.g. the parser/interpreter,
the generator and even the transfer component in a machine translation
system.
In fact LRL is a slight misnomer, since grammar rules can also be
written in the language and a parser is incorporated in the LKB system
in order to test lexical entries.
In designing the language we adopted a similar philosophy 
to that behind PATR-II (Shieber, 1986), in that the LRL is
intended to be sufficiently general to encode
a range of possible approaches to linguistic representation.
Like PATR-II, the LRL is based on the use of feature structures.
However, in contrast to PATR-II, feature structures are typed
in a manner similar to that proposed by Carpenter (1990, 1992).  
Feature structures must be
well-formed with respect to types and particular features will only be
appropriate to specified types and their subtypes.  
The type system only allows non-default inheritance;
we augment this with a
restricted concept of default inheritance from feature structures,
referred to as {\it psorts} in this context.  Default inheritance is
formalised in terms of default unification 
and is constrained by the type system.  
The LRL itself is a relatively `theory neutral' language ---
a type system has to be developed to instantiate it 
in order to use it for representation based on a particular linguistic
theory.
The LRL is described in detail in 
various papers in Briscoe {\it et al.} (in press) and also in
Copestake (1992).
Here we will not attempt a formal description of the LRL but
will give an informal overview, illustrated
with relevant examples.\footnote{The type system described in this
paper was developed following on from that used on the ACQUILEX project
as a whole, which was described in Copestake (1992), for example.
The new system is somewhat simpler, it is less directly related 
to dictionary definitions and the treatment of some aspects of noun
semantics has been improved.}
We will start by giving an example, which is intended to give an 
intuitive idea of the representation language and type system, and
then consider the LRL in slightly more detail.

The following is a description of feature structure which corresponds to
a lexical entry 
for {\it musician}:
\begin{laureldesc}
musician L\_0\_1\\
\> \verb+< > < lex-individual < >+\\
\> \verb+< QUALIA > < person_L_0_1 < QUALIA >+\\
\> \verb+< QUALIA : TELIC  > <= perform_L_0_2 < SEM > .+
\end{laureldesc}
The identifier, L\_0\_1, indicates that the
entry is intended to (roughly) correspond to the LDOCE sense {\it
musician 1}:
\begin{description}
\item[musician 1] a person who performs on a musical instrument \ldots
\end{description}
The feature structure into which this description expands is shown 
as an attribute-value matrix (AVM) in
Figure~\ref{musician}.
\begin{figure}
{\centering
\tiny
$\avmplus{\att{lex-count-noun}\\
         \attvaltyp{ORTH}{musician}\\
         \attvalshrunktyp{CAT}{noun-cat}\\
         \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                  \attval{IND}{\ind{0}}\avmplus{\att{obj}\\
                                       \attval{AGR}{\avmplus{\att{agr}\\
                                                \attvaltyp{NUM}{sg}}}}\\
                  \attvaltyp{PRED}{musician\_L\_0\_1}\\
                  \attval{ARG1}{\ind{0}}\\
                  \attvaltyp{PLMOD}{false}\\
                  \attvaltyp{QUANT}{true}}}\\
         \attval{QUALIA}{\avmplus{\att{human}\\
                  \attvalshrunktyp{AGENTIVE}{agentivestuff}\\
                  \attval{TELIC}{\avmplus{\att{strict-trans-sem}\\
                           \attval{IND}{\ind{2}}\ \ \myvaluebold{eve}\\
                           \attvaltyp{PRED}{and}\\
                           \attval{ARG1}{\avmplus{\att{verb-formula}\\
                                    \attval{IND}{\ind{2}}\\
                                    \attvaltyp{PRED}{perform\_L\_0\_2}\\
                                    \attval{ARG1}{\ind{2}}}}\\
                           \attval{ARG2}{\avmplus{\att{binary-formula}\\
                                    \attval{IND}{\ind{2}}\\
                                    \attvaltyp{PRED}{and}\\
                                    \attval{ARG1}{\avmplus{\att{p-agt-formula}\\
                                             \attval{IND}{\ind{2}}\\
                                             \attvaltyp{PRED}{p-agt}\\
                                             \attval{ARG1}{\ind{2}}\\
                                             \attval{ARG2}{\ind{0}}}}\\
                                    \attvalshrunktyp{ARG2}{p-pat-formula}}}}}\\
                  \attval{FORM}{\avmplus{\att{nomform}\\
                           \attvaltyp{ABSOLUTE}{indform}\\
                           \attvaltyp{RELATIVE}{individual}}}\\
                  \attvalshrunktyp{CONSTITUENCY}{nomconst}\\
                  \attval{OBJECT-INDEX}{\ind{0}}\\
                  \attval{PROPERTIES}{\avmplus{\att{creature-properties}\\
                           \attvaltyp{STATE}{solid\_a}\\
                           \attvaltyp{SEX}{gender}}}}}}$

}
\caption{Lexical entry for musician}
\label{musician}
\end{figure}


The expansion is due to the combination of the type system, which
defines the underlying `templates' for all feature structures, and
to (default) inheritance from psorts.
Lower case bold font indicates types (e.g. {\bf human}), 
upper case is used for features (e.g. {\feature qualia}),
in AVM diagrams,
descriptions and text.
Lower case typewriter font is used for  
psorts in descriptions and text (e.g. {\psort person\_L\_0\_1}, 
{\psort lex-individual}).
Reentrancy is indicated by a boxed integer in the AVM diagrams.
Some parts of the entry are
not shown fully expanded in this figure
--- this is indicated by a box round the type name.
The description specified states that {\psort musician\_L\_0\_1}
is to default inherit from the entire psort {\psort lex-individual}, 
that its qualia structure is default inherited from the qualia
structure of {\psort person\_L\_0\_1} and that the telic role is
non-default inherited from the semantics of {\psort perform\_L\_0\_2}.

The lexical entry consists of four main components.  The value for
{\feature orth} is a simple string representing the orthography.
The syntactic component is indicated by the feature {\feature cat}, 
but is shown unexpanded here.
We adopt a categorial approach to syntax, 
for details of which see Sanfilippo (in press).
{\feature sem} introduces the formal semantic structure,
which is encoded in a way which is basically equivalent to the lambda
calculus expression $\lambda x [{\bf musician\_L\_0\_1}(x)]$.
Agreement is specified on the indices, following Pollard and Sag 
(forthcoming).

The feature {\feature qualia} introduces the lexical semantic
structure.
The lexical semantic type of the entry is {\bf human} 
(see Figure~\ref{human}).
The telic role is shown in detail (although it is not completely expanded);
it has been instantiated with the semantics for the lexical
entry for {\it perform}.
Verb semantics are expressed in the type system as a whole in a
neo-Davidsonian representation making use of thematic roles
(see Sanfilippo, in press).  The formula given for
the telic role is equivalent to $\lambda e [{\bf perform\_L\_0\_2}(e)
\wedge {\rm agent}(e, x)]$ where $x$ is bound in the expression of
the semantics of the lexical entry as a whole so that 
${\bf musician\_L\_0\_1}(x)$. 
\begin{figure}
{\centering
\tiny
$\avmplus{\att{human}\\
         \attvalshrunktyp{AGENTIVE}{agentivestuff}\\
         \attvalshrunktyp{TELIC}{verb-sem}\\
         \attval{FORM}{\avmplus{\att{nomform}\\
                  \attvaltyp{ABSOLUTE}{indform}\\
                  \attvaltyp{RELATIVE}{(individual plural group)}}}\\
         \attvalshrunktyp{CONSTITUENCY}{nomconst}\\
         \attvaltyp{OBJECT-INDEX}{entity}\\
         \attval{PROPERTIES}{\avmplus{\att{creature-properties}\\
                  \attvaltyp{STATE}{solid\_a}\\
                  \attvaltyp{SEX}{gender}}}}$

}
\caption{Constraint on the lexical semantic type {\bf human}}
\label{human}
\end{figure}


\subsection{The type system}

The type system is the basis for setting up 
linguistic representations in the LRL.
The type hierarchy defines a partial ordering
on the types and specifies
which types are {\em consistent}.  Only feature structures with
mutually consistent types can be unified --- two types which are
unordered in the hierarchy are assumed to be inconsistent
unless the user explicitly specifies a common subtype.
Every {\em consistent} set of types  
has a unique greatest lower bound or
meet; when two feature structures are successfully unified 
the type of the resulting feature structure will be the meet of
their types.  
Thus, in the fragment of a type
hierarchy shown in Figure~\ref{typehier}, {\bf natural} and {\bf physical} are
consistent; unifying a feature structure of type {\bf natural} with one of type
{\bf physical} will result in a feature structure of type {\bf natural\_physical}.

\begin{figure}
\setlength{\unitlength}{0.8in}
{\centering
\begin{picture}(4, 2.6)(1.5, 0)
\put(5,3){\makebox(0,0){\bf top}}
\put(5,2.9){\line(-2, -1){0.7}}
\put(4,2.5){\makebox(0,0){\bf nomqualia}}
\put(4,2.4){\line(-2, -1){0.7}}
\put(4,2.4){\line(2, -1){0.7}}
\put(5,2){\makebox(0,0){\bf natural}}
\put(5,1.9){\line(-2, -1){0.7}}
\put(3,2){\makebox(0,0){\bf physical}}
\put(3,1.9){\line(-2, -1){0.7}}
\put(3,1.9){\line(2, -1){0.7}}
\put(2,1.5){\makebox(0,0){\bf artifact\_physical}}
\put(4,1.5){\makebox(0,0){\bf natural\_physical}}
\put(4,1.4){\line(0, -1){0.3}}
\put(4,1){\makebox(0,0){\bf creature}}
\put(4,0.9){\line(2, -1){0.7}}
\put(4,0.9){\line(-2, -1){0.7}}
\put(3,0.5){\makebox(0,0){\bf human}}
\put(5,0.5){\makebox(0,0){\bf animal}}
\end{picture}

}
\caption{A fragment of the lexical semantic type hierarchy}
\label{typehier}
\end{figure}


Our formalism differs somewhat from that described by Carpenter in
that we adopt a different notion of {\it well-formedness} of typed feature
structures (i.e. consistency of feature structures with the type system).
In the LRL, every type must have exactly one associated
feature structure which acts as a constraint on all feature structures
of that type; by subsuming all well-formed feature structures of that
type.  The constraint also defines which features are {\em
appropriate} for a particular type --- a well formed feature structure
may only contain appropriate features.  Constraints are inherited by
all subtypes of a type, but a subtype may introduce new features
(which will be inherited as appropriate features by all its subtypes).
A constraint on a type is a well-formed feature structure of that
type; all constraints must therefore be mutually consistent.
The constraint on the type {\bf human} is shown in 
Figure~\ref{human}: in effect the information expressed in this 
is inherited non-defeasibly 
by the qualia structure of
lexical entries such as that for {\it musician}.
The type system has to be completely specified before any
lexical entries can be expanded; 
this allows the well-formedness of lexical entries to be checked
but is too inflexible to be the sole means of inheritance.

\subsection{Psort inheritance}

To allow default inheritance and more flexible non-default inheritance, 
we introduce the concept of a {\em psort}; 
a feature structure from which another feature structure inherits
information, normally by default.
The hierarchical ordering on psorts (which
must be consistent with the type hierarchy) provides an order on
defaults.  Default inheritance is implemented by a version of default
unification (e.g. Carpenter, in press).  Multiple inheritance is
restricted to the case where
information inherited from different sources 
is consistent.  Non-default inheritance from psorts is also allowed; 
this is simply implemented using ordinary unification.
Default inheritance from a psort is indicated in the description
language by \verb+<+, non-default inheritance by \verb+<=+.

Psorts may correspond to lexical entries or be specially defined in order to
conveniently group some information. 
In the description for {\it musician} shown above {\psort lex-individual},
{\psort person\_L\_0\_1} and {\psort perform\_L\_0\_2} are all psorts;
the first is specially defined, the latter two are lexical entries.
Because of the condition that the type hierarchy and the
default inheritance hierarchy must be consistent, the default
inheritance specification also determines the type of the qualia structure
for {\it musician} to be {\bf human}, non-defeasibly.
The non-default inheritance from {\psort perform\_L\_0\_2} allows the
appropriate semantic structure to be copied to fill the {\feature
telic} role.
(Details of these psorts are shown in the appendix.)
Other lexical entries, for example that for {\it minstrel}, will
themselves inherit information taxonomically from 
the psort {\psort musician\_L\_0\_1} which is set up by the lexical entry.
In the remainder of this paper, we will consider how group nouns may
be represented in the LRL in a manner which is consistent with the
rest of the type system.

\section{Group nouns}
\label{group}

Group nouns, such as {\it band}, {\it crowd}, {\it quartet}, {\it
flock}, {\it management}
and {\it group} itself, 
are distinctive in English in that, when morphologically singular,
they behave in some respects like singular nouns and in others like plurals.
This manifests itself in several ways:
\begin{enumerate}
\item Singular or plural pronouns can be used:
\begin{ex}
The band played well tonight.
Its/their tour has sold out.
\end{ex}
\item Either singular or plural agreement with the verb
is possible (plural agreement with group nouns is, in general,
less common in American English):
\begin{ex}
That band play/plays well.
\end{ex}
In the case of group nouns which denote groups of humans, 
a relative clause is introduced by {\it who} if
plural agreement is used, and by {\it which} if it is not:
\begin{ex}
The band who get/*gets top billing at the festival 
receive/*receives \pounds 20,000.\\
The band which gets/*get top billing at the festival 
receives/*receive \pounds 20,000.
\end{ex}
\item Individual members can be referred to by using {\it one of} etc.
\begin{ex}
One of the band smashed her guitar.
\end{ex}
\end{enumerate}
The final criterion distinguishes between group nouns and those such
as {\it barracks} and {\it gallows} which can take either singular or
plural agreement (when referring to the same entity).  Note also that
unpluralised group nouns always take a singular determiner, even if
verbal agreement is plural.
\begin{ex}
This barracks is/*are new.\\
These barracks are/*is new.\\
That band has/have been playing well.
\end{ex}

However, there are other nouns which do not meet these criteria, even
though they refer to entities which can be regarded as being
made up of several discrete individuals.
For example, consider the LDOCE definition of {\it dolmen}:
\begin{description}
\item[dolmen] a group of upright stones supporting a large flat piece
of stone, built in ancient times in Britain and France
\end{description}
Despite the fact that a
{\it dolmen} can evidently be regarded as a group of entities, it
does not behave as a group noun; the following are all 
unacceptable:
\begin{ex}
\begin{subex}
The dolmen is on a mountain. *They're very eroded.
\end{subex}
\begin{subex}
*The dolmen have fallen down.
\end{subex}
\begin{subex}
*One of the dolmen fell down.
\end{subex}
\end{ex}
There is clearly a semantic distinction
between group and non-group nouns;
when a group noun is used
the individual components of the entity denoted are sufficiently
obvious that it can be referred to as though it were a plural
term.  
Collectives such as {\it terrace} and {\it range}, which 
denote groups of entities of a particular type and which usually appear with
{\it of} phrases ({\it terrace of houses}, {\it range of mountains}),
do share some of the behaviour of group nouns, however.
These nouns
always take singular agreement when morphologically singular
(at least when the {\it of} phrase is absent),
and thus are not group nouns by the 
first two tests, but they can meet the third, although only in
contexts where the individual members are explicitly mentioned.  
\begin{ex}
\begin{subex}
The house was one of a terrace.
\end{subex}
\begin{subex}
* One of the terrace had a green front door.
\end{subex}
\end{ex}
Example \exnum{0}{a} is taken from the Lancaster-Oslo/Bergen
(LOB) corpus; 
when checking for {\it one of}\, followed by a morphologically singular
noun phrase, this was 
the only example where the head of the NP was not 
a group noun by the agreement tests.
There is a
contrast between {\it terrace} 
and {\it group}, as the latter is not at all limited in the
semantic type of its {\it of} complement (e.g. {\it group of houses},
{\it group of statistics}, {\it group of actions}), but which 
refers to people when used without the {\it
of} phrase in an unmarked context.  

The singular/plural dual behaviour of true group nouns
to some extent corresponds to whether the 
predicate is seen as applying to the group as a whole or to its
individual members.  
\begin{ex}
The band was formed in 1977.\\
The team were killed in a plane crash.
\end{ex}
There is a tendency for singular agreement to be used when the group 
as an entity
is referred to, and for plural agreement to be used
when the individuals are concerned.
The examples above are odd when the agreement is changed:
\begin{ex}
? The band were formed in 1977.\\
? The team was killed in a plane crash.
\end{ex}

Sometimes differences in agreement alone suggest a semantic distinction.
In \exnum{+1}{a} the implication is that the committee 
as an entity gets the money, \exnum{+1}{b} suggests that it goes to the 
individual members and there is a possible distributive reading, forced in
\exnum{+1}{c}. Note that \exnum{+1}{d} is bad.
\begin{ex}
\begin{subex}
The committee gets \pounds 20,000 per annum.
\end{subex}
\begin{subex}
The committee get \pounds 20,000 per annum.
\end{subex}
\begin{subex}
The committee get \pounds 20,000 per annum each.
\end{subex}
\begin{subex}
? The committee gets \pounds 20,000 per annum each.
\end{subex}
\end{ex}
However, plural agreement with verb phrases which apparently refer to the
group as a single entity is quite normal in some contexts,
such as when referring to sports teams or clubs.
\begin{ex}
\begin{subex}
Forfar are a good side. (LOB corpus) 
\end{subex}
\begin{subex}
But there was to be no bargaining [~on players' contracts~]
as far as the club were concerned.  ({\it The Guardian})
\end{subex}
\end{ex}

It is useful to distinguish between ordinary group nouns and those
which refer generically, since the latter class involve 
some different problems which we will not discuss here.
Ordinary group nouns
form plurals in the normal way, 
(e.g. {\it bands}, {\it crowds}, {\it quartets}, {\it flocks}),
but others do not normally form plurals
because they refer generically (e.g. {\it aristocracy}, {\it clergy}),
or to an entity usually regarded as unique
(e.g. {\it admiralty}), although 
plurals are possible in phrases such as 
{\it the admiralties of England and France}.
The generic group nouns have dual group-entity/plural behaviour, 
but their plural behaviour parallels that of
bare plural noun phrases in `universal' position, in contrast to 
normal group nouns.  For example \exnum{+1}{a} implies \exnum{+1}{b}
but \exnum{+1}{c} does not imply \exnum{+1}{d}, but only \exnum{+1}{e}.
\begin{ex}
\begin{subex}
The clergy are badly paid.
\end{subex}
\begin{subex}
Clergymen are badly paid.
\end{subex}
\begin{subex}
The committee are badly paid.
\end{subex}
\begin{subex}
Committeemen are badly paid.
\end{subex}
\begin{subex}
The committeemen are badly paid.
\end{subex}
\end{ex}

In what follows we will make
the simplest assumption about the nature of the plural reading
of ordinary group nouns, which is that it is equivalent to a normal plural.
The plural reading corresponds to
an entity which can be regarded as the
sum of the members of the group, 
and has a qualia structure 
appropriate for a normal plural entity.
\footnote{In the formal semantics 
we treat the domain of individuals 
as having a lattice structure (Link, 1983).
The semantics assumed are based on work by Krifka (1987).
Plural individuals consist of a sum of ordinary individuals,
but there is no distinction in formal semantic type
between an ordinary individual and a plural one.
Ordinary singular count predicates, such as {\bf musician}$'$,
denote sets of non-plural individuals.  Plural predicates
are formed by taking the closure of the denotation of the singular 
predicate, e.g. $\clos${\bf musician}$'$.}
This straightforwardly accounts for the verbal and pronominal
agreement, and for
the use of partitives with the plural interpretation.
On this assumption, we should get both distributive and collective
plural readings.  
Distinguishing
the group reading and the collective plural reading is not easy but
there are examples such as 
\exnum{+1}{a} which should probably be treated as 
a collective plural, since the predicate refers to individual members
rather than the group entity.
Similarly \exnum{+1}{b} has a cumulative reading
(Scha 1983), where the committee members are distributed in some 
unspecified way between the cars.
\begin{ex}
\begin{subex}
The committee are arriving in a car.
\end{subex}
\begin{subex}
The committee are arriving in three cars.
\end{subex}
\end{ex}

We then have to address the question of relating the group and the
plural readings.
We will assume that
a group and the plural sum of its members are distinct
entities, and that the plural reading is produced from the group reading
by a process of logical metonymy, similar to that discussed in
section~\ref{qualia}.  
In this case, the instantiation involves the composition of the
entity rather than its purpose.
The metonymic account allows for the examples of
group nouns such as {\it club}, {\it committee} 
and {\it company},
where the entity denoted seems to have an existence independent of
its members, even when a 
purely extensional viewpoint is taken.
One can imagine a club, for example, which currently has no members
but nonetheless still exists as a legal entity.
This is problematic for theories which make the representation
the group entity dependent on its members, but does not pose 
any problems for the metonymic account. 
\footnote{The metonymic treatment
is less plausible with group nouns such
as {\it crowd} which cannot exist without members, and thus where 
the distinction between the group and its members has less
justification on a purely extensional treatment.
Landman (1989) has an extensive discussion of groups in the context of the
treatment of plurality.
For example, Landman treats the collective reading of
sentences such as \exnum{+1}{} as involving a group, rather than
the plural sum.  
\begin{ex}
John and Mary lifted a piano.
\end{ex}
Landman makes a type distinction between a 
group and the plural sum of its members.  
However, since group formation can iterate indefinitely, this leads to a 
proliferation of types.  Since we do not think that Landman's treatment
adequately accounts for the properties of group nouns such as {\it club},
we have not adopted it here.}

So this suggests
that in order to provide an adequate lexical semantics for group nouns,
information about their membership must be represented, 
in order to allow
appropriate semantic information to be associated with phrases such as
{\it one of the band}.
We associate this information with the
{\feature constituency}
role of the qualia structure.

It appears that group nouns in English
always refer to entities whose 
individual members are seen as capable of independent, agentive action, 
usually humans or other `higher' animals.  
We have tested this assumption in a preliminary way using LDOCE;
group nouns can, in theory,
be retrieved as a class quite simply, since 
they are marked in the dictionary by the grammar codes 
GC (group countable, e.g. {\it committee})
or GU (group uncountable, e.g. {\it Admiralty}).
Unfortunately the LDOCE 
coding is far from comprehensive in this case
({\it army}, {\it assembly},  {\it band}, {\it coven}
have no senses marked as being group nouns, for example)
and the GU code has been given to a considerable number of entries 
which would not be characterised as group nouns by the tests given above,
especially plural forms such as {\it letters} and {\it tactics}.  
We thus considered only nouns with grammar code GC, and excluded
the morphologically
plural forms {\it games}, {\it Olympic Games} and {\it vibes},
which also do not meet all the tests. 
The remaining senses all
refer to collections of humans or human organisations, or
(less frequently) animals, 
with the exceptions {\it fleet} and {\it convoy}\,,
where the individual entities are ships.\footnote{There may be a
connection here with the use of feminine gender
personal pronouns when referring to
ships, given that group nouns are normally
associated with humans and higher animals.}  
There are some group nouns 
which can refer to collections of people or
organisations which may themselves
be groups;
\begin{description}
\item[league$^2$ 3] a group of sports clubs or players \ldots
\end{description}
Thus grouping is not restricted to a single level.  

It thus seems that 
lexicalisation of a concept of a collection of entities
as a group nouns is restricted to a small semantic class of entities,
which we will provisionally limit to humans, organisations and animals, 
ignoring the ship examples for the time being,
since further work is necessary to more precisely delimit the class.

\subsection{Representing group denoting nouns in the LRL}

We can describe entries for group denoting nouns in the LRL, which
allow us to formalise most of the
aspects of their behaviour discussed above.
An entry for {\it band}, in the sense meaning a group of
musicians is shown in Figure~\ref{band-group}.
\begin{figure}
{\centering
\tiny
$\avmplus{\att{lex-count-noun}\\
         \attvaltyp{ORTH}{band}\\
         \attvalshrunktyp{CAT}{noun-cat}\\
         \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                  \attval{IND}{\ind{0}}\avmplus{\att{obj}\\
                                       \attval{AGR}{\avmplus{\att{agr}\\
                                                \attvaltyp{NUM}{sg}}}}\\
                  \attvaltyp{PRED}{band\_L\_3\_2}\\
                  \attval{ARG1}{\ind{0}}\\
                  \attvaltyp{PLMOD}{false}\\
                  \attvaltyp{QUANT}{true}}}\\
         \attval{QUALIA}{\avmplus{\att{human}\\
                  \attvalshrunktyp{AGENTIVE}{agentivestuff}\\
                  \attval{TELIC}{\avmplus{\att{strict-trans-sem}\\
                           \attval{IND}{\ind{2}}\ \ \myvaluebold{eve}\\
                           \attvaltyp{PRED}{and}\\
                           \attval{ARG1}{\avmplus{\att{verb-formula}\\
                                    \attval{IND}{\ind{2}}\\
                                    \attvaltyp{PRED}{perform\_L\_0\_2}\\
                                    \attval{ARG1}{\ind{2}}}}\\
                           \attvalshrunktyp{ARG2}{binary-formula}}}\\
                  \attval{FORM}{\avmplus{\att{nomform}\\
                           \attvaltyp{RELATIVE}{group}}}\\
                  \attval{CONSTITUENCY}{\avmplus{\att{groupconst}\\
                           \attvalshrunktyp{ELEMENTS}{human}}}\\
                  \attval{OBJECT-INDEX}{\ind{0}}}}}$

}
\caption{Lexical entry for {\it band}}
\label{band-group}
\end{figure}                   
This feature structure corresponds to the group entity reading for {\it band}.
Here we have assumed that number agreement is tightly linked to
the group/plural distinction, and thus agreement is specified as
{\bf sg}.  Alternatively it could be underspecified as {\bf num}
to allow for examples, 
such as those given earlier, where plural agreement is used
in sentences which seem on semantic grounds to
involve an uncoerced group entity.\footnote{Neither of these options
is completely satisfactory, of course.  We would like to say 
that, by default,
agreement is determined by the group/plural distinction, but that this
default may be overridden.  This is not possible in the current LRL,
since defaults are part of the description language and thus operate
only on the paradigmatic plane and do not affect
syntagmatic combination.}


The lexical semantic type of the entry is {\bf human}, but the values
for the features {\feature constituency} and 
{\feature form : relative} are specific to group denoting nouns.
The representation for the lexical semantics of
group denoting nouns has to be compatible with the rest of the type system.
Given the results above, which suggest that there are only
restricted semantic classes of group nouns, it clearly would be inappropriate
to parallel the entire existing lexical semantic type hierarchy 
with a group type hierarchy.  Furthermore much of the information
about group nouns will be comparable with
that about their individual members.
We therefore allow types such as {\bf human} to apply  
to both individuals and groups, and distinguish between the two
by specifying that the {\sc constituency} feature either takes type
{\bf nongroupconst} or {\bf groupconst}.  Only the latter has 
{\sc elements} as an appropriate feature.  The lexical semantics of the
plural sum of the
individuals making up a group noun is specified as the value of the
{\sc elements} feature. 
In the case of {\it band} the individuals involved are {\it
musicians}, thus the {\sc elements} slot is instantiated with the
qualia structure corresponding to the pluralised form of {\psort
musician\_L\_0\_1}.  
(In Figure~\ref{band-group} this is shown
unexpanded so only the type, {\bf human}, is apparent.)
The value of {\feature form : relative} is also specific to group
denoting nouns. 
In general {\feature form : relative} specifies individuation relative
to a predicate --- other possible values include {\bf individual}, {\bf
plural} and {\bf mass}.
  
The lexical entry given above does not
directly account for the plural reading of group nouns.
Our treatment of the group/members logical metonymy is very similar
to that of the entity/event coercion, but
in this case type coercion will occur in contexts where
a plural entity is required. 
We implement this 
in {\sc laurel} with a unary rule, {\psort group-to-plural},
which applies to 
a group denoting noun phrase.
Rules in the LRL are themselves feature structures, which can be taken
as describing the relationship between an input structure and an
output structure.  
The rule {\psort group-to-plural} is actually quite complex, since it 
has to apply to type-raised noun phrases.  It is given in full in the
appendix --- here we will summarise
its effects on the various parts of the sign:
\begin{itemize}
\item The orthography is unchanged.
\item The categorial syntactic structure remains of type {\bf
raised-np-cat}, 
but is changed so that it integrates appropriately with the
new semantics and qualia structure.
\item The formal semantics is set up so that it is essentially
equivalent to `the members of [ input NP ]' 
(e.g. {\it the members of the band}).
The operator {\bf membership} applies to the group entity, to give the
plural entity.
\item The output sign has plural agreement.
\item The qualia structure for the output sign is equal to the
value of\linebreak 
\verb+<+ {\tt QUALIA : CONSTITUENCY : ELEMENTS} \verb+>+ 
in the input sign.
This will have the {\feature form} appropriate for a plural entity.
\end{itemize}

The sign which would result from the application of 
{\psort group-to-plural}
to {\it the band} is shown in Figure~\ref{band-plural}.
This sign has obligatory plural agreement and denotes the plural
entity which consists of the members of the band.
The unary rule application is forced in contexts where a 
formally plural entity is required, for example
a partitive construction, such as {\it
one of}.  When this
is used with a group noun (e.g. {\it one of the band}) 
the unary rule is applied to the group to give a plural entity, and
the appropriate specification of the individuals involved
is then produced in much the same way as for the ordinary plural
(e.g. {\it one of the members of the band}).
\begin{figure}
{\centering
\tiny
$\avmplus{\att{nominal-sign}\\
         \attval{ORTH}{\avmplus{\att{complex-orth}\\
                  \attvaltyp{ORTH1}{the}\\
                  \attvaltyp{ORTH2}{band}}}\\
         \attvalshrunktyp{CAT}{raised-np-cat}\\
         \attval{SEM}{\avmplus{\att{binary-formula}\\
                  \attval{IND}{\ind{0}}\ \ \myvaluebold{entity}\\
                  \attvaltyp{PRED}{the}\\
                  \attval{ARG1}{\avmplus{\att{binary-formula}\\
                           \attval{IND}{\ind{1}}\avmplus{\att{dummy-or-obj}\\
                                                \attval{AGR}{\avmplus{\att{agr}\\
                                                         \attvaltyp{NUM}{pl}}}}\\
                           \attvaltyp{PRED}{the\_1}\\
                           \attval{ARG1}{\avmplus{\att{obj-noun-formula}\\
                                    \attval{IND}{\ind{2}}\avmplus{\att{obj}\\
                                                         \attval{AGR}{\avmplus{\att{agr}\\
                                                                  \attvaltyp{NUM}{sg}}}}\\
                                    \attvaltyp{PRED}{band\_L\_3\_2}\\
                                    \attval{ARG1}{\ind{2}}\\
                                    \attvaltyp{PLMOD}{false}\\
                                    \attvaltyp{QUANT}{true}}}\\
                           \attval{ARG2}{\avmplus{\att{binary-formula}\\
                                    \attval{IND}{\ind{1}}\\
                                    \attvaltyp{PRED}{membership}\\
                                    \attval{ARG1}{\ind{1}}\\
                                    \attval{ARG2}{\ind{2}}}}}}\\
                  \attval{ARG2}{\ind{3}}\avmplus{\att{formula}\\
                                       \attval{IND}{\ind{0}}\\
                                       \attvaltyp{PRED}{logical-pred}\\
                                       \attvaltyp{ARG1}{sem}}}}\\
         \attvalshrunktyp{QUALIA}{human}}$

}
\caption{Coerced form of {\it the band}}
\label{band-plural}
\end{figure}


The representation of lexical semantic information about the individuals
which comprise the group thus allows the plural-like aspects of the
behaviour of group nouns to be accounted for.  
The {\psort group-to-plural} rule 
specifies the qualia structure of the resulting plural
entity according to the composition described in the 
{\sc constituency} feature and the
effect on the lexical semantics thus
parallels the effect on the logical representation. 

\section{The use of MRDs}
\label{extract}

To some extent, lexical entries such as those
shown in this paper can be acquired
semi-automatically from LDOCE.  
To do this we make use of a combination of information from the
definition and from the LDOCE grammar codes.
For example, consider again the definition of {\it musician}
and the corresponding LRL entry:
\begin{description}
\item[musician 1] a person who performs on a musical instrument \ldots
\end{description}
\begin{laureldesc}
musician L\_0\_1\\
\> \verb+< > < lex-individual < >+\\
\> \verb+< QUALIA > < person_L_0_1 < QUALIA >+\\
\> \verb+< QUALIA : TELIC  > <= perform_L_0_2 < SEM > .+
\end{laureldesc}
Syntactic information can be derived from LDOCE's grammar
codes; in this case {\it musician} corresponds to an ordinary count
noun, which results in the inheritance from {\psort
lex-individual}.  We will not discuss extraction of information from
grammar codes in detail here.

Noun definitions can be split into a {\em genus} and
{\em differentia}; 
the genus can usually be taken to be the syntactic head of the
definition.
Here the genus term is taken to be (a particular sense of) {\it person}.
The basis for our use of noun
dictionary definitions as a source of lexical semantic information
is that, in general,
we can specify that 
entries inherit lexical semantic information by default from the entry
corresponding to their genus term.
The differentia may augment or override the information inherited from
the genus term.

We can automatically
extract genus terms reliably from noun definitions such as that
above (Vossen, 1990)
and lexically disambiguate them  
(semi-)automatically (Copestake, 1990).\footnote{The disambiguation
procedure is semi-automatic in that a series of heuristics are used to
determine the sense of the genus term, and the user is asked to
confirm the choice made by the heuristics in some cases, to avoid
large numbers of lexical entries inheriting information incorrectly.
When creating hierarchies of concrete nouns from LDOCE, the user checks about
5\% of the entries.}
Extracting information from the differentia is more difficult.
It is possible,
once the semantic type of a sense is known, 
to use the type as a template to guide analysis of the
definitions, but 
a considerable amount of work is required
to achieve this, and in ACQUILEX so far
this has only been attempted on limited
classes of definitions (see, for example,  Ageno {\it et
al.}, 1992; Vossen, 1992).
Thus the telic role for the entry above was
manually specified.  In general, associating information manually with
lexical entries which are frequently used as psorts
is an effective way of acquiring information, since 
inheritance will result in a large number 
of other entries being instantiated.
However there are many special
cases where definitions do not straightforwardly yield genus terms 
which can be interpreted as psorts.   This is extensively
discussed in Vossen and Copestake (in press); here I will concentrate
on the particular case of group nouns.
    
\subsection{Dictionary definitions of group nouns}

It is usually assumed that 
dictionary definitions should, in general, 
be substitutable, in context, 
for the word being defined (e.g. Landau, 1984).
Because of this principle of substitutability, definitions of
group nouns in dictionaries such as LDOCE will normally be 
group denoting noun phrases.  In some cases 
the genus term will be a relatively specific group noun, for example:
\begin{description}
\item[ crew $^{1}$ 3 ] a rowing team
\end{description}
Such definitions can be treated as illustrated above: 
the entire qualia structure is
default inherited from the entry for the genus sense, {\it team 2}.
\begin{laureldesc}
crew L\_1\_3\\
\> \verb+< > < lex-group < >+\\
\> \verb+ < QUALIA > < team_L_0_2 < QUALIA >.+
\end{laureldesc}

However there is another class of definitions where the genus phrase
is of the form `DET {\it group of} N ' and the noun is 
principally being defined in terms of its members, for example:
\begin{description}      
\item[band$^{3}$ 2] a group of musicians \ldots
\end{description}
Such cases pose more problems, since there is very little
semantic information that can be inherited from {\it group}.
As illustrated with the example of {\it dolmen}, given earlier,
the use of {\it group of} does not 
necessarily indicate a noun which is group denoting 
in the technical sense.
In other cases, a group noun may be defined using a plural genus
term, for example:
\begin{description}      
\item[audience 1]  the people listening to or watching a performance,
speech, television show, etc.
\end{description}
In this case, the definition cannot be substituted for the {\it
audience} in contexts where it is used with singular agreement
or refers to the group as a whole.
\begin{ex}
The audience were very noisy tonight.\\
The people listening to the performance were very noisy tonight.\\
The audience was very noisy tonight.\\
\mbox{}*The people listening to the performance was very noisy tonight.\\
The audience was tiny.\\
\mbox{}*The people listening to the performance was tiny.
\end{ex}
(Presumably the lexicographer felt that it was better to use
{\it people} than {\it group of people}, for example, which 
perhaps suggests a greater cohesion between
the individuals than is appropriate here.)
For such examples, a representation has to be built based on
information about the individual members, rather than 
about the group as a whole.

Clearly, given the type system
outlined earlier, information about the type of a 
group's members makes it possible to infer the type of the group noun.
If the members are of type {\bf human} then the group as a whole will
be of type {\bf human}, and so on.
Furthermore the {\feature constituency}
role can be instantiated with the qualia structure for the members.
So the following
entry could be produced for {\dword band\,$^{3}$ 2}:
\begin{laureldesc}
band L\_3\_2\\
\> \verb+ < > < lex-group < >+\\
\> \verb+ < QUALIA > =+ {\bf human}\\
\> \verb+ < QUALIA : CONSITUENCY : ELEMENTS >+\\
\> \verb!           < ( musician_L_0_1 + plural ) < QUALIA >.!
\end{laureldesc}
Here \verb!( musician_L_0_1 + plural )! indicates that the rule for
plural formation is applied to the psort {\psort musician\_L\_0\_1}
before inheritance of the qualia structure takes place (see appendix).

However this leaves some information unspecified, in particular the {\sc telic}
role.  We assume that this can be inherited from the 
{\sc telic} role of the members,
so the {\sc telic} role of {\dword band\,$^{3}$ 2} 
is inherited from {\dword musician} for example, 
\begin{laureldesc}
\> \verb+ < QUALIA : TELIC >+\\
\> \verb+        < musician_L_0_1 < QUALIA : TELIC >.+
\end{laureldesc}
Adding this to the description above we get a specification which will
expand out into the feature structure shown in
Figure~\ref{band-group}.

The inheritance of the telic role needs some justification, since
in general usage it is not possible to 
assume that a group as a whole has a property even if  
all its members have that property, and the property is one
which could hold of the group as a whole.
For example:
\begin{quote}
All the members of the committee are against the poll tax.
\end{quote}
does not entail that:
\begin{quote}
The committee is against the poll tax.
\end{quote}
Inheritance of the telic role might also be problematic.
There could be a group of musicians who got together to play football,
for example, so:
\begin{quote}
The King's Road football team is a group of musicians.
\end{quote}
could be true, in which case the purpose of the group described would
not be equivalent to that lexically specified by {\it musician}.
However such examples are exceptional, and 
in the special case of
dictionary definitions, if a group is
defined in terms of its members it can be taken to inherit appropriate
properties from them; we have not found any counter-examples to this in LDOCE
so far.
Intuitively, it seems unlikely that a dictionary would define
a group in terms of its members, if they had a purpose or function 
which was distinct from that of the group.  Even if a
concept such as the musicians' football team
were lexicalised, the lexicographer would have to specify the function
of the group explicitly to avoid being misleading,
and thus the default inheritance from its
members' telic role would be overridden.  

Thus,
on the assumption that we can recognise the class of group nouns,
and distinguish their members in the definitions, we can 
(semi-)automatically extract
reasonably adequate entries, such as that shown for {\it band}.
This is quite straightforward for nouns which are specified as GC in the
LDOCE grammar coding scheme and which have entries of the form,
`DET {\it group of} N '.
However there are problems in recognising the class of group nouns.
As we mentioned earlier, the grammar coding scheme
has not been applied consistently to group nouns.
There are a variety of
ways in which group nouns can be defined, and some of these patterns
of definitions can also be used for non-group nouns.  Although we can
use a range of heuristics to identify candidate group nouns, these
rely on certain assumptions, for example that any noun which denotes
more than one person, but which is not marked as plural, is likely to
be a group noun.  Clearly, we need other sources of information in
order to attempt comprehensive extraction.

Other MRDs could be used to enhance our existing data,
but since
sense-to-sense mapping on independent dictionary sources is a hard
problem, which itself requires some form of LKB, we could at
best determine that a headword has some sense which is marked as being
a group noun, and use this as an additional heuristic.
Corpora could also
be used, but a massive amount of data is needed to have a significant chance of
finding the less frequent group nouns used in a context where their
distinctive behaviour is apparent.  There are about 30 occurrences of
{\it crowd} as a singular noun in the approximately 1.2 million word LOB
corpus, and only one of these is in a context where singular/plural
agreement can be distinguished.
Checking a range of nouns manually
for dual agreement on corpora of sufficient size
would be an extremely labour intensive task without tools to
partially parse selected sentences. 
Even then, the problem of sense distinction still remains ---
the skills of the professional lexicographer are really needed here.
We believe that the way forward for computational lexicology and
lexicography is collaboration with lexicographers and dictionary
publishers, giving them the tools with which to instantiate LKBs,
which could then be used for linguistic research, for NLP, and for the
production of conventional dictionaries. 

\section{Conclusion}
\label{conc}
We have used the example of group nouns in this paper to illustrate
the way in which we attempt to
combine ideas and
techniques from lexical semantics, lexicography and knowledge
representation.
Although the fragment shown here is integrated into a system which
treats other complex aspects of lexical semantics, such as logical
metonymy and sense extension, much more work is clearly needed
to produce a comprehensive treatment of noun
semantics which would properly test our approach.  
Furthermore there
are some issues which appear to require modifications to the LRL, in
particular with respect to the treatment of defaults.
We are currently
investigating richer representational frameworks, which should, 
for example, allow a better treatment of agreement than that shown
here.  
Briscoe {\it et al.} (this volume) discusses one way in which a more
general notion of defaults can be combined with a feature structure
based representation language.


% first argument - i.e. #1 is always author
% #2 is title
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% 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.}
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#3,} #5.}
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#5.}
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{\bf #4}.}
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#3,} #4, pp.~#5.}
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#3,} #4, ,#5, pp.~#6.}
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#3,} #4.}
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#3,} #4, #5.}
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\newcommand{\procartnoppnoplace}[4]{\item #1 (#4) `#2', {\it Proceedings of the
#3}.}
% article in proceedings without known page numbers without place
% where meeting happened
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#3,} pp.~#4.}
% article in proceedings where the venue is not known
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% #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
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% Put refs here
% 
%\end{list}



\section{References}

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

\procart{Ageno, A., I. Castellon, G. Rigau, H. Rodriguez, M.F.~Verdejo, 
M.A.~Marti, M.~Taule}
{SEISD: an environment for extraction of semantic information from
on-Line dictionaries}
{3rd Conference on Applied Natural Language Processing (ANLP-92)} 
{Trento, Italy}
{253--255}
{1992}

\bookart{Briscoe, E. J.}
    {Lexical issues in natural language processing}
    {39--68}
    {Natural language and speech}
    {E. Klein and F. Veltman}
    {Springer-Verlag}
    {1991}

\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}

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

\procart{Carpenter, R.}
    {Typed feature structures: inheritance, (in)equality and extensionality}
    {First International Workshop on 
     Inheritance in Natural Language Processing}
    {Tilburg, The Netherlands} 
    {9--18}
    {1990}

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

\bookartnopp{Carpenter, R.}
    {Skeptical and credulous default unification with applications to
templates and inheritance}
    {Inheritance, defaults and the lexicon}
    {E.~J.~Briscoe, A.~Copestake and V.~de~Paiva}
    {Cambridge University Press}
    {in press}


\procart{Copestake, A.}
     {An approach to building the hierarchical element of 
      a lexical knowledge base from a machine readable dictionary}
     {First International Workshop on
      Inheritance in Natural Language Processing}
     {Tilburg, The Netherlands}
     {19--29}
     {1990}

\procart{Copestake, A.}
{The ACQUILEX LKB: representation issues in semi-automatic
acquisition of large lexicons}
{3rd Conference on Applied Natural Language Processing (ANLP-92)}
{Trento, Italy}
{88--96}
{1992} 

\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}
     {1991}

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

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


\book{Landau, S.~I.}
     {Dictionaries: the art and craft of lexicography}
     {Scribner, New York}
     {1984}

\journart{Landman, F.}
    {Groups I + II}
    {Linguistics and Philosophy}
    {12 (5,6)}
    {559--606, 723--744}
    {1989}

\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}

\book{Procter, P. (editor)}
    {Longman Dictionary of Contemporary English}
    {Longman, England}
    {1978}

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

\bookartnopp{Sanfilippo, A.}
    {LKB encoding of lexical knowledge from machine-readable dictionaries}
    {Inheritance, defaults and the lexicon}
    {E.~J.~Briscoe, A.~Copestake and V.~de~Paiva}
    {Cambridge University Press}
    {in press}   

\unpub{Scha, R.J.H.}
    {Logical foundations for question answering}
    {PhD thesis}
    {1983}

\book{Shieber, S.~M.}
{An introduction to unification-based approaches to grammar}
{CSLI Lecture Notes 4, Stanford CA}
{1986}

\unpub{Vossen,  P.}
{A parser-grammar for the meaning descriptions of LDOCE}
{Links Project Technical Report 300-169-007, Amsterdam University}
{1990} 

\procartnopp{Vossen, P.}
{An empirical approach to automatically construct a knowledge base
from dictionaries}
{5th EURALEX}
{Tampere, Finland}
{1992}

\bookartnopp{Vossen, P. and A. Copestake}
    {Untangling definition structure into knowledge representation}
    {Inheritance, defaults and the lexicon}
    {E.~J.~Briscoe, A.~Copestake and V.~de~Paiva}
    {Cambridge University Press}
    {in press}

\bookart{Zwicky, A. M. and J. M. Sadock}
    {Ambiguity tests and how to fail them}
    {1--36}
    {Syntax and Semantics IV}
    {J.~P.~Kimball}
    {Academic Press, New York}
    {1975}

\end{list}

\newpage
\section*{Appendix}

In this appendix we give more detailed descriptions of the structures
used in the examples given in the paper.  

\subsection*{Types, psorts and lexical entries}

The following structure shows the type, {\bf lex-count-noun}, which
is the type of all the lexical entries described:
\begin{center}
\tiny
$\avmplus{\att{lex-count-noun}\\
         \attvaltyp{ORTH}{orth}\\
         \attvalshrunktyp{CAT}{noun-cat}\\
         \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                  \attval{IND}{\ind{0}}\avmplus{\att{obj}\\
                                       \attval{AGR}{\avmplus{\att{agr}\\
                                                \attvaltyp{NUM}{number}}}}\\
                  \attval{PRED}{\ind{1}}\ \ \myvaluebold{logical-pred}\\
                  \attval{ARG1}{\ind{0}}\\
                  \attvaltyp{PLMOD}{boolean}\\
                  \attvaltyp{QUANT}{boolean}}}\\
         \attval{QUALIA}{\avmplus{\att{nomqualia}\\
                  \attvaltyp{AGENTIVE}{nomagent}\\
                  \attvalshrunktyp{TELIC}{verb-sem}\\
                  \attval{FORM}{\avmplus{\att{nomform}\\
                           \attvaltyp{ABSOLUTE}{real-form}\\
                           \attvaltyp{RELATIVE}{countable}}}\\
                  \attvalshrunktyp{CONSTITUENCY}{nomconst}\\
                  \attval{OBJECT-INDEX}{\ind{0}}}}}$
\end{center}
For current purposes the important
points about this type are:
\begin{enumerate}
\item A value of {\bf true} for the feature {\feature plmod} in the semantics 
is intended  to be interpreted as equivalent to modifying the predicate by the
closure operator $\clos$.  The value {\bf false} indicates that the
predicate is not so modified.
\item The feature {\feature quant} encodes the cumulative/quantised
distinction (see Krifka 1987).
\item The type {\bf countable} given as the value of the relative form
in the qualia structure has several subtypes --- those relevant here
are {\bf individual}, {\bf plural} and {\bf group}.
\end{enumerate}

All noun lexical entries are specified as inheriting from one of a
range of psorts which specify their mode of individuation.  
Those
relevant here are {\psort lex-individual}, {\psort lex-plural}
and {\psort lex-group}:
\begin{laureldesc}
lex-individual\\
\> \verb+< > = +{\bf lex-count-noun}\\
\> \verb+< QUALIA : FORM : RELATIVE > =+ {\bf individual}\\
\> \verb+< SEM : IND : AGR : NUM > =+ {\bf sg}\\
\> \verb+< SEM : PLMOD > =+ {\bf false}\\
\> \verb+< SEM : QUANT > =+ {\bf true} .
\end{laureldesc}

\begin{laureldesc}
lex-plural\\
\> \verb+< > =+ {\bf lex-count-noun}\\
\> \verb+< QUALIA : FORM : RELATIVE > =+ {\bf plural}\\
\> \verb+< SEM : QUANT > =+ {\bf false}\\
\> \verb+< SEM : IND : AGR : NUM > =+ {\bf pl}.
\end{laureldesc}

\begin{laureldesc}
lex-group\\
\> \verb+< > < lex-individual < >+\\
\> \verb+< QUALIA : FORM : RELATIVE > =+ {\bf group}\\
\> \verb+< QUALIA : CONSTITUENCY > =+ {\bf groupconst}.
\end{laureldesc}
Since these are psorts, values may be overridden.  This allows for
nouns like {\it barracks} or {\it gallows} which are treated as
basically individual denoting, although they may take plural agreement.

The relevant parts of the lexical entries for {\it person} and {\it
perform} from which the entry for {\it musician} inherits are shown
below.
\begin{center}
\tiny

$\avmplus{\att{lex-count-noun}\\
         \attvaltyp{ORTH}{person}\\
         \attvalshrunktyp{CAT}{noun-cat}\\
         \attvalshrunktyp{SEM}{obj-noun-formula}\\
         \attval{QUALIA}{\avmplus{\att{human}\\
                  \attval{AGENTIVE}{\avmplus{\att{agentivestuff}\\
                           \attvaltyp{ORIGIN}{basic}}}\\
                  \attvalshrunktyp{TELIC}{verb-sem}\\
                  \attval{FORM}{\avmplus{\att{nomform}\\
                           \attvaltyp{ABSOLUTE}{real-form}\\
                           \attvaltyp{RELATIVE}{individual}}}\\
                  \attvalshrunktyp{CONSTITUENCY}{nomconst}\\
                  \attval{OBJECT-INDEX}{\ind{1}}\avmplus{\att{obj}\\
                                       \attval{AGR}{\avmplus{\att{agr}\\
                                                \attvaltyp{NUM}{sg}}}}\\
                  \attval{PROPERTIES}{\avmplus{\att{creature-properties}\\
                           \attvaltyp{STATE}{solid\_a}\\
                           \attvaltyp{SEX}{gender}}}}}}$
\end{center}

\begin{center}
\tiny

$\avmplus{\att{strict-trans-sign}\\
         \attvaltyp{ORTH}{perform}\\
         \attvalshrunktyp{CAT}{strict-trans-cat}\\
         \attval{SEM}{\avmplus{\att{strict-trans-sem}\\
                  \attval{IND}{\ind{0}}\ \ \myvaluebold{eve}\\
                  \attvaltyp{PRED}{and}\\
                  \attval{ARG1}{\avmplus{\att{verb-formula}\\
                           \attval{IND}{\ind{0}}\\
                           \attval{PRED}{\ind{1}}\ \ \myvaluebold{perform\_L\_0\_2}\\
                           \attval{ARG1}{\ind{0}}}}\\
                  \attval{ARG2}{\avmplus{\att{binary-formula}\\
                           \attval{IND}{\ind{0}}\\
                           \attvaltyp{PRED}{and}\\
                           \attval{ARG1}{\ind{2}}\avmplus{\att{p-agt-formula}\\
                                                \attval{IND}{\ind{0}}\\
                                                \attvaltyp{PRED}{p-agt}\\
                                                \attval{ARG1}{\ind{0}}\\
                                                \attval{ARG2}{\avmplus{\att{obj}\\
                                                         \attval{AGR}{\avmplus{\att{agr}\\
                                                                  \attvaltyp{NUM}{number}}}}}}\\
                           \attval{ARG2}{\ind{3}}\avmplus{\att{p-pat-formula}\\
                                                \attval{IND}{\ind{0}}\\
                                                \attvaltyp{PRED}{p-pat}\\
                                                \attval{ARG1}{\ind{0}}\\
                                                \attval{ARG2}{\avmplus{\att{obj}\\
                                                         \attval{AGR}{\avmplus{\att{agr}\\
                                                                  \attvaltyp{NUM}{number}}}}}}}}}}}$
\end{center}

\subsection*{Unary rules}

The examples in the paper use two unary rules, {\psort group-to-plural} and
{\psort plural}.  Unary rules in the LRL are feature
structures of type {\bf unary-rule}.  This has two
features {\feature 1} and {\feature 0} which indicate the input and
output of the rule respectively.  
Unary rules are used to encode type shifting, morphological rules and
sense extensions --- the only distinction between these types of
rule is that morphological rules are the only ones which involve
orthographic changes and that type shifting rules may involve phrasal
signs, whereas morphological and sense extension rules are limited 
to lexical signs.
Thus {\psort group-to-plural} is a type shifting rule which takes a
phrasal sign as input (in this case an NP) but {\psort plural}
is a morphological rule.
The sign for the unshifted NP, {\it the band}, is shown in
Figure~\ref{band-np}.  It can be seen that this will unify with the 
the input section of the unary rule {\psort group-to-plural}
which is shown in Figure~\ref{gtop}, giving the feature structure
shown in Figure~\ref{band-plural} as output. 

\begin{figure}
{\centering
\tiny

$\avmplus{\att{nominal-sign}\\
         \attval{ORTH}{\avmplus{\att{complex-orth}\\
                  \attvaltyp{ORTH1}{the}\\
                  \attvaltyp{ORTH2}{band}}}\\
         \attvalshrunktyp{CAT}{raised-np-cat}\\
         \attval{SEM}{\avmplus{\att{binary-formula}\\
                  \attval{IND}{\ind{0}}\ \ \myvaluebold{entity}\\
                  \attvaltyp{PRED}{the\_1}\\
                  \attval{ARG1}{\avmplus{\att{obj-noun-formula}\\
                           \attval{IND}{\ind{1}}\avmplus{\att{obj}\\
                                                \attval{AGR}{\avmplus{\att{agr}\\
                                                         \attvaltyp{NUM}{sg}}}}\\
                           \attvaltyp{PRED}{band\_l\_3\_2}\\
                           \attval{ARG1}{\ind{1}}\\
                           \attvaltyp{PLMOD}{false}\\
                           \attvaltyp{QUANT}{true}}}\\
                  \attval{ARG2}{\ind{2}}\avmplus{\att{formula}\\
                                       \attval{IND}{\ind{0}}\\
                                       \attvaltyp{PRED}{logical-pred}\\
                                       \attvaltyp{ARG1}{sem}}}}\\
         \attval{QUALIA}{\ind{3}}\avmplus{\att{human}\\
                              \attvalshrunktyp{AGENTIVE}{agentivestuff}\\
                              \attvalshrunktyp{TELIC}{strict-trans-sem}\\
                              \attval{FORM}{\avmplus{\att{nomform}\\
                                       \attvaltyp{ABSOLUTE}{real-form}\\
                                       \attvaltyp{RELATIVE}{group}}}\\
                              \attval{CONSTITUENCY}{\avmplus{\att{groupconst}\\
                                       \attvaltyp{PARTICLES}{string}\\
                                       \attvalshrunktyp{ELEMENTS}{human}\\
                                       \attvaltyp{UNITQUANTITY}{string}}}\\
                              \attval{OBJECT-INDEX}{\ind{1}}\\
                              \attvalshrunktyp{PROPERTIES}{creature-properties}}}$

}
\caption{AVM diagram for the phrasal sign {\it the band}}
\label{band-np}
\end{figure}

\begin{figure}
{\centering
\tiny

$\avmplus{\att{unary-rule}\\
         \attval{0}{\avmplus{\att{nominal-sign}\\
                  \attval{ORTH}{\ind{0}}\ \ \myvaluebold{orth}\\
                  \attval{CAT}{\avmplus{\att{raised-np-cat}\\
                           \attval{RESULT}{\ind{1}}\ \ \boxvaluebold{sign}\\
                           \attval{DIRECTION}{\ind{2}}\ \ \myvaluebold{direction}\\
                           \attval{ACTIVE}{\avmplus{\att{sign}\\
                                    \attvaltyp{ORTH}{orth}\\
                                    \attval{CAT}{\avmplus{\att{complex-cat}\\
                                             \attval{RESULT}{\ind{1}}\\
                                             \attval{DIRECTION}{\ind{2}}\\
                                             \attvalshrunktyp{ACTIVE}{nominal-sign}}}\\
                                    \attval{SEM}{\ind{3}}\ \ \boxvaluebold{formula}}}}}\\
                  \attval{SEM}{\avmplus{\att{binary-formula}\\
                           \attval{IND}{\ind{4}}\ \ \myvaluebold{entity}\\
                           \attvaltyp{PRED}{the}\\
                           \attval{ARG1}{\ind{5}}\avmplus{\att{binary-formula}\\
                                                \attval{IND}{\ind{6}}\avmplus{\att{dummy-or-obj}\\
                                                                     \attval{AGR}{\avmplus{\att{agr}\\
                                                                              \attvaltyp{NUM}{pl}}}}\\
                                                \attvaltyp{PRED}{logical-pred}\\
                                                \attvalshrunktyp{ARG1}{formula}\\
                                                \attval{ARG2}{\avmplus{\att{binary-formula}\\
                                                         \attvaltyp{IND}{entity}\\
                                                         \attvaltyp{PRED}{membership}\\
                                                         \attval{ARG1}{\ind{6}}\\
                                                         \attval{ARG2}{\ind{7}}\ \ \myvaluebold{entity}}}}\\
                           \attval{ARG2}{\ind{3}}}}\\
                  \attval{QUALIA}{\ind{8}}\avmplus{\att{nomqualia}\\
                                       \attvaltyp{AGENTIVE}{nomagent}\\
                                       \attvalshrunktyp{TELIC}{verb-sem}\\
                                       \attval{FORM}{\avmplus{\att{nomform}\\
                                                \attvaltyp{ABSOLUTE}{real-form}\\
                                                \attvaltyp{RELATIVE}{plural}}}\\
                                       \attvalshrunktyp{CONSTITUENCY}{nomconst}\\
                                       \attvaltyp{OBJECT-INDEX}{entity}}}}\\
         \attval{1}{\avmplus{\att{nominal-sign}\\
                  \attval{ORTH}{\ind{0}}\\
                  \attvalshrunktyp{CAT}{raised-np-cat}\\
                  \attval{SEM}{\ind{5}}\\
                  \attval{QUALIA}{\avmplus{\att{nomqualia}\\
                           \attvaltyp{AGENTIVE}{nomagent}\\
                           \attvalshrunktyp{TELIC}{verb-sem}\\
                           \attval{FORM}{\avmplus{\att{nomform}\\
                                    \attvaltyp{ABSOLUTE}{real-form}\\
                                    \attvaltyp{RELATIVE}{group}}}\\
                           \attval{CONSTITUENCY}{\avmplus{\att{groupconst}\\
                                    \attvaltyp{PARTICLES}{string}\\
                                    \attval{ELEMENTS}{\ind{8}}\\
                                    \attvaltyp{UNITQUANTITY}{string}}}\\
                           \attvaltyp{OBJECT-INDEX}{entity}}}}}}$

}
\caption{The {\psort group-to-plural} type-shifting rule}
\label{gtop}
\end{figure}
 



The plural rule which was referred to in Section~\ref{extract}
is shown in Figure~\ref{plural} for completeness.
\begin{figure}
{\centering
\tiny
$\avmplus{\att{morph-rule}\\
         \attval{0}{\avmplus{\att{lex-noun-sign}\\
                  \attval{ORTH}{\avmplus{\att{complex-orth}\\
                                  \attval{ORTH1}{\ind{7}}\ \ \myvaluebold{orth}\\
                                  \attval{ORTH2}{\verb!+!s}}}\\
                  \attvalshrunktyp{CAT}{noun-cat}\\
                  \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                           \attval{IND}{\ind{0}} \avmplus{\att{obj}\\
                                                \attval{AGR}{\avmplus{\att{agr}\\
                                                         \attvaltyp{NUM}{pl}}}}\\
                           \attval{PRED}{\ind{1}}\ \ \myvaluebold{logical-pred}\\
                           \attval{ARG1}{\ind{0}}\\
                           \attvaltyp{PLMOD}{true}\\
                           \attvaltyp{QUANT}{false}}}\\
                  \attval{QUALIA}{\avmplus{\att{nomqualia}\\
                           \attval{AGENTIVE}{\ind{2}}\ \ \myvaluebold{nomagent}\\
                           \attval{TELIC}{\ind{3}}\ \ \boxvaluebold{verb-sem}\\
                           \attval{FORM}{\avmplus{\att{nomform}\\
                                         \attvaltyp{RELATIVE}{plural}}}\\
                           \attval{CONSTITUENCY}{\ind{5}}\ \ \boxvaluebold{nomconst}\\
                           \attval{OBJECT-INDEX}{\ind{0}}}}}}\\
         \attval{1}{\avmplus{\att{lex-noun-sign}\\
                  \attval{ORTH}{\ind{7}}\\
                  \attvalshrunktyp{CAT}{noun-cat}\\
                  \attval{SEM}{\avmplus{\att{obj-noun-formula}\\
                           \attval{IND}{\ind{6}} \avmplus{\att{obj}\\
                                                \attval{AGR}{\avmplus{\att{agr}\\
                                                         \attvaltyp{NUM}{number}}}}\\
                           \attval{PRED}{\ind{1}}\\
                           \attval{ARG1}{\ind{6}}\\
                           \attvaltyp{PLMOD}{false}\\
                           \attvaltyp{QUANT}{true}}}\\
                  \attval{QUALIA}{\avmplus{\att{nomqualia}\\
                           \attval{AGENTIVE}{\ind{2}}\\
                           \attval{TELIC}{\ind{3}}\\
                           \attvalshrunktyp{FORM}{nomform}\\
                           \attval{CONSTITUENCY}{\ind{5}}\\
                           \attval{OBJECT-INDEX}{\ind{6}}}}}}}$

}
\caption{Rule for plural formation}
\label{plural}
\end{figure}

\end{document}










