In this paper, we present a new mathematical framework in which disjunctive feature structures are defined as directed acyclic hypergraphs. Disjunction is defined in the feature structure domain, and not at the syntactic level in feature descriptions. This enables us to study properties and specify operations in terms of properties of, or operations on, hypergraphs rather titan in syntactic terms. We illustrate the expressive power of this framework by defining a class of disjunctive feature

more »

... uctures with interesting properties (factored normal form or FNF), such as closure under factoring, unfactoring, unification, and generalization. Unification, in particular, has the intuitive appeal of preserving as much as possible the particular factoring of the disjunctive feature structures to be unified. We also show that unification in the FNF class can be extremely efficient in practical applications.