And all this conceptual material must be organized into a grammatical surface form. By using these LTAG structures, SPUD always works with concrete grammatical surface forms. Each tree is paired with logical formulae that, by referring to a rich discourse model, characterize the semantic and pragmatic contribution that the tree makes to the sentence. By keeping track of these contributions as it builds the sentence, SPUD is able to assess the shared information that the sentence uses to identify discourse entities and the new information that the sentence adds about them. The order of adding content is flexible, allowing varied sentences without complicated search.
Grammatical knowledge is stated once only, inside the generator.
It enables efficient descriptions that refer implicitly to parameters from the context. It enables efficient descriptions that exploit the hearer's ability to recognize inferential links to material elsewhere in the sentence. These advantages make SPUD a natural generation system to use to formulate natural and concise output for dialogue interfaces to independent applications. Matthew Stone and Christine Doran. Sentence Planning as Description Using Tree-Adjoining Grammar.