Normalization of Semantic Graphs
At the level of semantic relations, we are interested in finding the semantic links hidden in the syntax of a sentence. This involves, among other things, normalizing semantic structures across a wide range of paraphrases. The goal is achieved by taking the output of the preceding analysis components and modifying it with a “concept grammar,” written in PLNLP. The rules of this grammar are similar in form to the rules of preceding components; but they operate on different aspects of the common information structure, analyzing the relations between nodes in the sentence graph, and normalizing semantic structures and lexical relationships in a variety of syntactic domains, without losing access to the surface syntactic differences. This chapter shows how, starting from the argument structure output from PEGASUS, the concept grammar produces semantic graphs that preserve the broad-coverage, broad-domain characteristics of the entire system.
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