The content of the SYN-STRUC zone of a lexicon entry is an indication of where the lexeme may fit into the syntactic parse of a sentence. In addition, this zone provides the basis of the syntax-semantics interface. The information contained in this zone essentially amounts to an underspecified piece of a syntactic parse of a typical sentence using the lexeme; this piece contains the lexeme in question, and may include information from any number of embedded levels (but typically not more than two) above or below the current lexeme. The information included reflects those levels and elements of the syntactic parse which the current lexeme syntactically selects for; in the current model, verbs select for all their arguments, modifiers select for their heads, prepositions select for their objects as well as for their node of attachment, etc. The SYN-STRUC zone thus determine such things as subcategorization (optionality is indicated, otherwise obligatoriness assumed), complements allowed, etc.
In the SYN-STRUC zone, we place variables at the ROOT positions
selected for by the lexeme in question, which is identified by the
variable var0. Subsequently numbered variables (var1, var2, ...) identify
other syntactic nodes with which the current lexeme has syntactic or semantic
dependencies. For example, the pattern below is appropriate for any regular monotransitive
verb:
((root var0) (subj ((root var1) (cat n))) (obj ((root var2) (cat n))))
For instance, in our example sentence, while processing the
``adquirir'' lexicon entry, ``Grupo Roche'' will be bound to var1 as
the SUBJ, while ``Dr. Andreu'' will be bound to var2. If a SYN-STRUC
requires a syntactic pattern not found in the current sentence, then
that word sense is not used.
The variable bindings introduced in the SYN-STRUC provide an interaction with the meaning pattern from the SEM zone in that certain portions of the meaning pattern for a phrase or clause are regularly and compositionally determined by the semantics of the components (Principle of Compositionality); the structure of the resulting meaning pattern is determined not only by the semantic meaning patterns of each of the components, but also by their syntactic relationship in the SYN-STRUC zone.