The Head-Driven Phrase Structure Grammar (HPSG) is a grammar theory developed by Pollard and Sag (1985). It uses a uniform formalism and is organized in a modular way which makes it attractive for Natural language processing.
... have a female householder with no husband present, and 15.9% are non-families. 13.0% of all households are made up of individuals and 5.2% have someone living alone who ...