Esfinge at CLEF 2008: Experimenting with Answer Retrieval Patterns. Can they help?

Esfinge is a general domain Portuguese question answering system which has been participating at QA@CLEF since 2004. It uses the information available in the “official” document collections used in QA@CLEF (newspaper text and Wikipedia), but additionally it also uses information from the Web as an additional resource when searching for answers. Where it regards the use of external tools, Esfinge uses a syntactic analyzer, a morphological analyzer and a named entity recognizer. This year an alternative approach to retrieve answers was tested: whereas in previous years, search patterns were used to retrieve relevant documents, this year a new type of search patterns was also used to extract the answers themselves. Besides that we took advantage of the main novelty introduced this year by QA@CLEF organization which was that the systems could return up to three answers for each question, instead of the single answer allowed in previous editions. This enabled the investigation about how good were the second and third best answers returned by Esfinge (when the first answer is not correct). The experiments revealed that the answer retrieval patterns created for this participation improve the results, but only for definition questions. Regarding the study of the three answers returned by Esfinge, the conclusion was that when Esfinge answers correctly a question, it does so usually with its first answer.