Senseval-3 logic forms: A system and possible improvements

Senseval 3 Logic Forms: A System and Possible Improvements Altaf Mohammed, Dan Moldovan, and Paul Parker Language Computer Corporation Richardson, TX 75080 {altaf, moldovan, parker}@languagecomputer.com Abstract Logic Forms, particular powerful logic representations presented in Moldovan and Rus (2001), are simple yet highly ef- fective. In this paper, the structure of Logic Forms and their generation from input text are described. The results of an evaluation comparing the Logic Forms generated by hand with those generated automatically are also reported. Finally, we suggest some improvements to the representation used in the LFI task based on our results. 1 Introduction Logic Forms are first order logic representations of natural language text. The notation is very close to the natural language. A Logic Form is a collection of predicate instances derived from text. A detailed description of the notation is pre- sented in Moldovan and Rus (2001). Logic Forms can be utilized by a wide variety of applications. A Logic Prover (Rus, 2002; Moldovan et al., 2003) utilizing the axioms gen- erated by the Logic Form generation system boosts the performance of the Question Answer- ing system. The Prover essentially takes as input the Logic Forms of the question and one or more answers and then proceeds to justify (and rank) the answers based on (i) world knowledge axi- oms, and (ii) NLP axioms. The Logic Prover de- veloped at Language Computer Corporation has increased the performance of the QA system by 30%. 2 Automatic Generation of Logic Forms 2.1 Parse Tree Construction Logic Forms are derived from the output of a syntactic parser. The first step is the identifica- tion of word collocations (based on those identi- fied by WordNet (Miller, 1995)). The parser then proceeds to identify (i) parts of speech of indi- vidual words, and (ii) syntactic structure of the text, based on grammar rules. It also differenti- ates active verb constructs from passive ones. The output is a parse tree. We also include in the parse tree (i) word senses, based on WordNet, and (ii) named-entity tags (Surdeanu and Hara- bagiu, 2002). Named-entity tags are tags associ- ated with a word or group of words, indicating that they belong to a particular category, for in- stance, currency, time, date, place, human, etc. The word senses from the parse tree are simply included in the Logic Form as is (for subsequent use in applications), while the named-entity tags are additionally used in the generation of Logic Forms. 2.2 Logic Form Generation First we identify independent arguments (those arguments which are generated anew for certain predicates). These include arguments for nouns, Association for Computational Linguistics for the Semantic Analysis of Text, Barcelona, Spain, July 2004 SENSEVAL-3: Third International Workshop on the Evaluation of Systems verbs (action/eventuality only), and compound nouns and coordinating conjunctions (for both of these, only the result argument (or the first one)). Independent arguments are also generated for certain adjectival phrases and/or determiners in the rare cases when they do not qualify a noun phrase, but stand all …

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