FINITE-STATE UNIFICATION AUTOMATA AND RELATIONAL LANGUAGES

We define the new notion of a (finite-state) unification automaton, a device for finite-state recognition of relational languages by means o f unification transitions. Words in such a language are formed by comp osing base relations, and have the general form r(i1)(x(j1), x(k1))... r(in)(x(jn), x(kn)) for some n. Generation of such languages by regard ing Horn clauses as grammers has been considered before, but to the be st of our knowledge, recognizing such languages by suitably designed a utomata is a new approach. The main result presented is a pumping lemm a, forming a necessary condition for finite-state recognizability. Som e example results about such automata are given. (C) 1994 Academic Pre ss, Inc.