The PUCRS-PLN Group Participation at CLEF 2006

This paper presents the 2006 participation of the PUCRS-PLN Group in CLEF Monolingual Ad Hoc Task for Portuguese. We participated with the TR+ Model based on nominalization, binary lexical relations (BLR), Boolean queries, and the evidence concept. Our alternative strategy for lexical normalization, the nominalization, is the transformation of a word (adjective, verb, or adverb) into a semantically corresponding noun. BLRs, which identify relationships between nominalized terms, capture phrasal cohesion mechanisms, like those that occur between subject and predicate, subject and object (direct or indirect), noun and adjective or verb and adverb. In our strategy, an index unit may be a single term or a BLR, and we adopt the evidence concept, i.e., the index unit weighting depends on the occurrence of phrasal cohesion mechanisms, besides the frequency of occurrence. We detail here these features, which implement lexical normalization and term dependence in an information retrieval system.