Typed Feature Structures System (TFS) 6.1
Type: Constraint-based Representation Formalism
Contacts: Martin C. Emele (
Platforms: Common Lisp
Publications: TFS publications

The Typed Feature Structure (TFS) representation formalism is anattempt to provide a synthesis of several of the key concepts ofunification-based grammar formalisms (feature structures), knowledgerepresentation languages (inheritance) and logic programming (logicalvariables and declarativity). The inheritance-based constraintarchitecture embodied in the TFS system integrates two computationalparadigms: the object-oriented approach offers complex,recursive, possibly nested, record objects represented as typedfeature structures with attribute-value restrictions and (in)equalityconstraints, and multiple inheritance; the relational programmingapproach offers declarativity, logical variables, non-determinism withbacktracking, and existential query evaluation. The interpreter of theformalism is described as a term rewriting system based on typeunfolding where unification of typed feature structures is used todetect inconsistencies between a query and the constraints imposed bythe feature type system.

The grammar writer organizes unification grammars as inheritancenetworks of typed feature structures. Complex linguistic structuresare described by means of recursive type constraints which correspondto class definitions in object-oriented formalisms. The use of anobject-oriented methodology with inheritance is very attractive fornatural language processing and offers a number of advantages such asabstraction and generalization, information sharing, modularity andreusability of descriptions. Through the development of a wide varietyof different applications it has been demonstrated that the formalismis flexible enough and well suited to represent the principles andparameters approach of modern computational linguistic theories. Inparticular, it has been successfully used for the encoding of HPSGgrammar fragments and a bilingual machine translation system based onthe shared-contents approach. Last Modified Tue Mar 10 17:40:34 1998