Reference no: EM131715300

Question: Draw a picture of the subsumption semilattice corresponding to the feature structures in Example. Be sure to include the most general feature structure [].

Example: FEATURES STRUCTURES IN THE GRAMMAR

Our primary purpose in introducing feature structures and unification has been to provide a way to elegantly express syntactic constraints that would be difficult to express using the mechanisms of context-free grammars alone. Our next step, therefore, is to specify a way to integrate feature structures and unification operations into the specification of a grammar. This can be accomplished by augmenting the rules of ordinary context-free grammars with attachments that specify feature structures for the constituents of the rules, along with appropriate unification operations that express constraints on those constituents. From a grammatical point of view, these attachments will be used to accomplish the following goals:

- To associate complex feature structures with both lexical items and instances of grammatical categories.

- To guide the composition of feature structures for larger grammatical constituents based on the feature structures of their component parts.

- To enforce compatibility constraints between specified parts of grammatical constructions.