A Grammar Formalism and Cross-Serial Dependencies

First we define a unification grammar formalism called the Tree Homomorphic Feature Structure Grammar. It is based on Lexical Functional Grammar (LFG), but has a strong restriction on the syntax of the equations. We then show that this grammar formalism defines a full abstract family of languages, and that it is capable of describing cross-serial dependencies of the type found in Swiss German.Comment: 19 pages uuencodet gnu-compressed PostScript format. A previous version of this paper is printed in the proceedings from the joint ELSNET/COMPULOG-NET/EAGLES workshop Computational Logic for Natural Language Processing (CLNLP95) in Edinburgh in April 199

Computing with Features as Formulae

This paper extends the approach to feature structures developed in Johnson (1991a), which uses Schönfinkel-Bernays' formulae to express feature structure constraints. These are shown to be a disjunctive generalization of Datalog clauses, as used in database theory. This paper provides a fixed-point characterization of the minimal models of these formulae that serves as the theoretical foundation of a forward-chaining algorithm for determining their satisfiability. This algorithm, which generalizes the standard attribute-value unification algorithm, is also recognizable as a nondeterministic variant of the semi-naive bottom-up algorithm for evaIuating Datalog programs, further strengthening the connection between the theory o]: feature structures and database