Feature structures are inherently partial in the information they provide. Based on the type inheritance ordering, we can order feature structures based on how much information they provide. This ordering is referred to as the subsumption ordering. The notion of subsumption, or information containment, can be used to define the notion of unification, or information combination. Unification conjoins the information in two feature structures into a single result if they are consistent and detects an inconsistency otherwise.