Feature Structures --- Bundles of information expressed as pairs of features and values. Values can be atomic (symbols like '+' or 'thick' or types like adj) or feature structures themselves.
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Feature Structures --- Bundles of information expressed as pairs of features and values. Values can be atomic (symbols like '+' or 'thick' or types like adj) or feature structures themselves.
HPSG --- Head-driven Phrase Structure Grammar. A framework or general theory of formal syntax. The formalism and general theory developed in the course textbook are derived from HPSG, but we can't say they are HPSG, because a) there isn't one completely shared version of HPSG across the research community and b) the framework in the textbook is simplified for pedagogical purposes.
Saturation --- This is part of the idea that lexical heads enter the syntax with a set of requirements of what else should appear. Moving up the tree, as they find these other phrases, those requirements are 'canceled off' or 'saturated'. Inspired by the same metaphor from chemistry as 'valence'.
Head/Headedness --- The idea that constituents have many of their properties determined by some distinguished word inside of them (the "head").