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Is a formal specification complete ?

Is a formal specification complete ?

By `formal' we mean a machine-readable description of what is correct or incorrect behaviour. A complete specification might describe all allowable behaviours and prohibit all remaining behaviours, but most formal definitions today are not complete in this sense. For instance, a definition that consists of of a list of safety assertions and a few liveness assertions might still allow all sorts of behaviours that the designer knows are wrong. He can go on adding more assertions, but when does he stop ?

One might define a 'complete specification' as one that describes all observable behaviours. Such a specification does not restrict or prescribe the internal implementation in black box terms since this is not observable.

When testing an IP block, can we compute coverage somehow: e.g. What percentage of rule disjuncts held as dominators (on their own) ?

Or, e.g. What (inverse log) percentage of reachable state space was spanned?

There are no well-accepted coverage metrics for formal specifications. We could measure what percentage of rule disjuncts held as dominators (on their own) ? There is no clear definition of 100 percent coverage.

(C) 2008-10, DJ Greaves, University of Cambridge, Computer Laboratory.