A FeatureStructure is a set of one or more FeatureSpecifications. A FeatureStructure is a kind of information structure, a container or data structure, used to group together qualities or features of some object. In a grammatical feature system, a FeatureStructure holds the grammatical information associated with some linguistic unit. In a typed feature system, a FeatureStructure has an associated type, usually a PartOfSpeech. [Shieber 1986; Maxwell, Simons, and Hayashi 2000].