The lexicon is a list of clauses lex(Word,Sign), associating a word (or sequence of words) with a specific sign.
Constraint-based grammars in general, and lexicalist constraint-based grammars in particular, tend to store lots of grammatical information in the lexicon. This is also true for the OVIS2 grammar. A lexical entry for a transitive verb, for instance, not only contains information about the morphological form of this verb, but also contains the features SC and SUBJ for which quite detailed constraints may be defined. Furthermore, for all lexical signs it is the case that their semantics is represented by means of a feature-structure. This structure can also be quite complex. To avoid massive reduplication of identical information in the lexicon, the use of inheritance is therefore essential.
In figure 3, we illustrate the use of inheritance in the lexicon. All lexical entries for verbs have a number of properties in common, such as the fact that they are of type v, and take a normal (non-locative and non-temporal) NP as subject. This is expressed by the template v(V). Intransitive verbs ( iv(V)) can now be characterised syntactically as verbs which do not subcategorise for any (non-subject) complements. Transitive verbs ( tv(V)) subcategorise for an NP with accusative case. The templates intransitive(Pred,Sign) and transitive(Pred,Sign), finally, combine the syntactic and semantic properties of intransitive and transitive verbs. The variable Pred is used in the semantics to fix the value of the predicate defined by a particular verb. A limited form of non-monotonic inheritance is supported (see Carpenter  and Bouma  for more general approaches). For instance, `weather' verbs require the dummy pronoun het ( it) as subject, but behave otherwise as intransitive verbs. This can be expressed by letting weather_v inherit from iv, with the exception of the value of the NFORM attribute of (head of the list containing) the subject, which is assigned an exceptional value. The attribute-value matrices for the templates iv(V) and tv(V) are:
The lexicon itself (i.e. the predicate lex/2) is defined in
terms of the predicates entry, inflection and