Feature cooccurrence restrictions

Generalized Phrase Structure Grammar (GPSG) uses Feature cooccurrence restrictions (FCRs) to formulate well-formedness conditions for feature structures. As GPSG takes feature structures to be arbitrary sets of feature specifications, it is necessary to block the combination of feature specifications which from a linguistic point of view make no sense. Most FCRs are formulated as implications.

Many theories of phonological features also apply FCRs: pairs of features, or pairs of features together with their values, that cannot cooccur within a segment.

Examples
Only verbal catgories can contain the feature vform: [VFORM] $$\rightarrow$$ [+V, -N]

Phrasal catgories cannot contain the feature subcat: [BAR 2] $$\rightarrow$$ $$\neg$$ [SUBCAT]

The vocalic fatures [+high] and [+low] cannot cooccur: [+high] $$\rightarrow$$ [-low] && [+low] $$\rightarrow$$ [-high]

Comments
Modern unification-based grammar formalisms like Head-Driven Phrase Structure Grammar use typed feature structures instead.

Other Languages

 * German Feature cooccurrence restrictions (de)