Unification of disjunctive feature descriptions is important for efficient unification-based parsing. This paper presents constraint projection, a new method for unification of disjunctive feature structures represented by logical constraints. Constraint projection is a generalization of constraint unification, and is more efficient because constraint projection has a mechanism for abandoning information irrelevant to a goal specified by a list of variables. These works are based on graph unification rather than on term unification. Graph unification has the advantage that the number of arguments is free and arguments are selected by labels so that it is easy to write a grammar.
