Tree Adjoining Grammar


Tree Adjoining Grammar

Tree-adjoining grammars (TAG) sind Grammatiken, die von Aravind Joshi eingeführt wurden und in der Computerlinguistik und bei der Verarbeitung von natürlichen Sprachen verwendet werden.

TAGs ähneln kontextfreien Grammatiken, verwenden aber einen Baum als Element. Knoten eines Baums werden durch andere Bäume ersetzt.

Die Regeln in einer TAG (sogenannte auxiliary trees) sind besondere Bäume, bei denen die Wurzel und eines der Blätter mit dem gleichen Symbol gekennzeichnet sind.

TAGs werden als schwach kontext-sensitiv beschrieben; sie sind also stärker als kontext-freie Grammatiken, aber schwächer als kontext-sensitive Grammatiken in der Chomsky-Hierarchie. Daher sind sie stark genug, um natürliche Sprachen abzubilden, aber auch schwach genug, um noch effizient parsebar zu sein.

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