Adding Semantics for Solving ‘PP Attachment’ in Spanish

Abstract

This paper describes a semantic module called DESPRE (DESambiguador de PREposiciones, or Disambiguator of prepositions) that solves the prepositional phrase attachment for Spanish and complements the syntactic analysis (based in tags and syntactic rules) of project FreeLing. Syntactic analysis is not enough to correctly disambiguate prepositions and attach each prepositional phrase to the appropriate head. This is because, depending on the context, the same preposition conveys different meanings. DESPRE analyzes the preposition and its surroundings, assigning to it its correct sense; once the preposition sense is disambiguated, parsing rules can more easily determine which the right head is, thus building the correct dependency tree. In this manner, with the help of the preposition semantics, the sentence is disambiguated and the prepositional phrase is correctly attached. DESPRE uses an ontology with semantic frames (for each prepositional sense) to disambiguate and solve prepositional phrase attachment. We have added new rules to the FreeLing dependency parser to handle the different preposition senses. Thus, DESPRE, the modified version of FreeLing, uses syntactic and semantic analysis. Several examples show the potential effectiveness of DESPRE, which was able to correctly  attach prepositional phrases that the syntactic analysis of Freeling alone could not.