We introduce a typed feature logic system providing both universal implicational principles as well as definite clauses over feature terms. We show that such an architecture supports a modular encoding of linguistic theories and allows for a compact representation using underspecification. The system is fully implemented and has been used as a workbench to develop and test large HPSG grammars. The techniques described in this paper are not restricted to a specific implementation, but could be added to many current feature-based grammar development systems.

We present a new approach to HPSG processing: compiling HPSG grammars expressed as type constraints into definite clause programs. This provides a clear and computationally useful correspondence between linguistic theories and their implementation. The compiler performs offline constraint inheritance and code optimization. As a result, we are able to efficiently process with HPSG grammars without having to hand-translate them into definite clause or phrase structure based systems.