Terminology Finite-State Preprocessing for Computational LFG

Terminology Finite-State Preprocessing for Computational LFG Caroline Brun Xerox Research Centre Europe 6, chemin de Maupertuis 38240 Meylan France Caroline.Brun@xrce.xerox.com Abstract This paper presents a technique to deal with multiword nominal terminology in a compu- tational Lexical Functional Grammar. This method treats multiword terms as single to- kens by modifying the preprocessing stage of the grammar (tokenization and morphological anal- ysis), which consists of a cascade of two-level finite-state automata (transducers). We present here how we build the transducers to take ter- minology into account. We tested the method by parsing a small corpus with and without this treatment of multiword terms. The number of parses and parsing time decrease without affect- ing the relevance of the results. Moreover, the method improves the perspicuity of the analy- ses. 1 Introduction The general issue we are dealing with here is to determine whether there is an advantage to treating multiword expressions as single tokens, by recognizing them before parsing. Possible advantages are the reduction of ambiguity in the parse results, perspicuity in the structure of analyses, and reduction in parsing time. The possible disadvantage is the loss of valid analy- ses. There is probably no single answer to this issue, as there are many different kinds of mul- tiword expressions. This work follows the inte- gration 1 of (French) fixed multiword expressions like a priori, and time expressions, like le 12jan- vier 1988, in the preprocessing stage. Terminology is an interesting kind of multiword expressions because such expressions are almost but not completely fixed, and there is an in- tuition that you won't loose many good anal- I This integration has been done by Fr~d6rique Segond. yses by treating them as single tokens. More- over, terminology can be semi or fully automat- ically extracted. Our goal in the present paper is to compare efficiency and syntactic coverage of a French LFG grammar on a technical text, with and without terminology recognition in the preprocessing stage. The preprocessing consists mainly in two stages: tokenization and morpho- logical analysis. Both stages are performed by use of finite-state lexical transducers (Kartun- hen, 1994). In the following, we describe the in- sertion of terminology in these finite-state trans- ducers, as well as the consequences of such an insertion on the syntactic analysis, in terms of number of valid analyses produced, parsing time and nature of the results. We are part of a project, which aims at developing LFG gram- mars, (Bresnan and Kaplan, 1982), in paral- lel for French, English and German, (Butt et al., To appear). The grammar is developed in a computational environment called XLE (Xe- rox Linguistic Environment), (Maxwell and Ka- plan, 1996), which provides automatic parsing and generation, as well as an interface to the preprocessing tools we are describing. 2 Terminology Extraction The first stage of this work was to extract termi- nology from our corpus. This corpus is a small French technical text of 742 sentences (7000 words). As we have at our disposal parallel aligned English/French texts, we …

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