ABSTRACT
For the purposes of this book we focus on NLP tasks relative to semantic information extraction. Semantic information identied in natural language text is represented by the notion of semantic relations. In the eld of NLP, semantic relations or semantic roles or thematic roles refer to the relation of a constituent to the main verb in a clause. Semantic relations may be either general, application-independent constructs or specic, domain/application dependent ones. The main semantic relations are: AGENT, EXPERIENCER, PATIENT, INSTRUMENT, CAUSE, LOCATION, PURPOSE, SOURCE, and PATH. For example, in the sentence, “The hunter red at the jackrabbit,” the “hunter” is the AGENT and the “jackrabbit” is the PATIENT of the action.
