Lexicon Design Using a Paradigmatic Approach

Lexicon Design Using a Paradigmatic Approach Cristian Dumitrescu Research Institute for Informatics Alex. Averescu Blvd. 8-10, 71316 Bucharest 1, Romania, Fax: 653095 Abstract The paper describes models for representation and meth6d~ to handle lexicograp.hic_structures supplied .by the MORPHO-2 sfftem. It was built to m_~n.~ge mono "hfigual lexicons and to incorporate lexical proce~in~ 1 Introduction Most advaneed systems for natural lanL~3ge " prgcessing use powerfullexicons and mg_rp_ho-lexical proc~ssi~g.~ ehvironments. • The s!r4. em descn])ed b~low enables monolifigual lexicon han- dling and incorporat ~ morpho-lexical processes (i.e. word-form anaanaFysis" and sy~he.sis'_..~sl a_t _at lexicon, leveL At present,., it works as a component otthe/U _RES envaronment fQi building natural lan- guage app.lications Ohlis and Cristea,. _19&_5). S~c6 in our appr_oach .the morphological processes .obey a paradigmatic morphology (Ttt~.- 19~), word-f6rms analysis and synthesis take into account, ont~ grammatical endings.(wlj.'ch in- dudes both desinences and sutr@s. ) and the lexicons handled by MORPHO-2 system are root- or lemma-oriented. By. lexicon we don't mean only a collection of roots and associated features. At lexicon level we also encounter the control structures needed for morphological prow.ssi~, morpho-lexical acquisition menus, root modification rules, word-forms synthesis rules, etc. The services provided by the system may be ch¢.~ified accord- ing to the follox;vhag, g o,o,~: morphological model .design, lexi.cal st6ck building and morpho-lexicfil pro6essing(Dumitrescu, 1991). 2 Morphological Model Design In order to build the mo.rphological model, an inte~ated environ- ment which allows edi'-tmg , viewing and comping the mor- pholoffical model descrioti6n, is available to the De-fining the morp.ho].ogical model takes place m several steps, during " .whiCh the lin~afist hfis to specify the following; a) the categories, subcategories, features and their values, in a hierarchical manner b) the paradigmatic descriptions c) the default feature specifications associated to each paradigmatic description d) the lemma - entry correspondence, for each paradig- matic description e) the inflectional paradigms and root detection rules. . The hierarchical de~crip0.'on of features is achieved by cor- relating several feature sp&ifications.+A feature s pe:#fication is given re, the fo .rna of a,(fe~ture: v~lu 9 ) pair.. We ~ a paradig- matic 9escripdon. a. hierarchical description build of several stmple (teature: value) pairs. F.lgu}e 1 ~ W-~nts, in the forrg_ of an incomplete tree, the hierarchical deki-ipfign Of features trom the morbhologi.cal model.for the Romanifin ~ . By tree trave.rsal, all paradig- matic dgscriptions of the m.oclel ff~ay b~y generated. Each non-terminal node contains a single feature speck'_ca- tion. The leaf nodes .may contain one or more teature (#ca- tions: A._gzordi~g " .to the su~r selection criteria, whib..h is a~ plmd when xasmng a non-terminal node, we can distingm~a Y'2 COMMON PROPER IND CJ ,,, GER /- .... /. ~[/.~ ~s~ / ". PL 1 2 N/A G/D F'~mre 1 Hierarchical description of features O-lOOSE nodes(when only one successor is selected) or V'OREACH nodes (_when the individual selection of each successor is re- quired). In the figure, a V'OREACH node is outlined by a curve drawn over the emerging edges: By trave~ the tree across the longest …

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