Inheritance and Constraint-Based Grammar Formalisms

We describe an approach to unification grammars that integrates two paradigms: the objectoriented approach, which offers multiple inheritance, complex objects with role-value restrictions and role-values equality, querying as subsumption; the relational programming approach, which offers declarativity, logical variables, nondeterminism with backtracking, and existential queries. This approach is embodied in a constraint-based object-oriented formalism. The interpreter of the formalism is described as a term rewriting system based on unification of typed feature structures. The grammar writer organizes unification grammars as inheritance networks of typed feature structures. Complex linguistic structures are described by means of recursive type constraints. We illustrate the use of inheritance networks with two examples: an HPSG example where implication (as used for "principles") is modeled using inheritance and an example of bilingual transfer where the minimal amount of information needed for the translation is specified at different levels of generalization.