Parametric types for typed attribute-value logic

Parametric polymorphism has been combined with inclusional polymorphism to provide natural type systems for Prolog (DH88), HiLog (YFS92), and constraint resolution languages (Smo89), and, in linguistics, by HPSG-like grammars to classify lists and sets of linguistic objects (PS94), and by phonologists in representations of hierarchical structure (Kle91). This paper summarizes the incorporation of parametric types into the typed attribute-value logic of (Car92), thus providing a natural extension to the type system for ALE (CP96). Following (Car92), the concern here is not with models of feature terms themselves, but with how to compute with parametric types, and what diferent kinds of information one can represent relative to a signature with parametric types, than relative to a signature without them. This enquiry has yielded a more flexible interpretation of parametric types with several specific properties necessary to conform to their current usage by linguists and implementors who work with feature-based formalisms.