A High-level Morphological Description Language Exploiting Inflectional Paradigms

A High-level Morphological Description Language Exploiting Inflectional Paradigms Peter Anick and Suzanne Artemieff Digital Equipment Corporation 111 Locke Drive, LMO2d/DI2 Marlboro, MA 01752 anick@aiag.enet.dec.cnm Abstract A high-level language lor the description of inflectional morphology is presented, in which the organization of word lormation rules into an ii~herilance hierarchy of paradigms allows lora natural encoding of the kinds of nfles typically pre~uted in grammar txroks. We show how tim language, composed of orthographic rides, word formation rules, and paradigm inheritance, can be com- piled into a run-time data structure for efficient morpho- logical analysis and generation with a dynamic secondary storage lexicon. 1 Introduction Pedagogical grmnmar Nalks typically organize their de- scriptinns of the inflectiomd morphology of a langtmge in terms of paradigms, groups of rnlas which characterize the inflectional behavior of some subset of the language's vocabulary. A French grannnar may divide verbs into the first, secoud, and third conjugations; German grammars speak of "weak" and "strong" verbs; Spanish grammars classify verbs by their infiuitival endings, etc. The family nf word forms that each v(x:abuhu'y item may have can thus he describexl by a combination of a ba~ stem (such as the "citation lbrm" used to index words in a dictionary) and the paradigm the word belongs to. Irregular words, which exhibit belu~viors not completely captured by gen- eral paradigms, often tend to be partially describable by reference to regular parudigmatic patterns. The word formation rules that comprise a paradigm are usually expressed in terms of a sequence of stem change and affixation operations. For example, one French text- Imok [NEBEL741, in describing first conjugation verbs, shows how to fi)rm present tense forms nsing the inliniti- val stem with its "er" suffix rmnoved. Future tense is tormed by appending ',fffixes to the fifll infinitival stem, while the stem of the imperfect tense is Ionnd by taking the first person plural of the present tense and dropping the "ons". Ill addition to such word formation roles, there are spelling change rules wbich describe variations ill spelling, often ctmditioned by file phonologic~d or ortho- graphic context th which a word lbrnlation rule is applied. While the above characterization of morphological behav- ior is a huniliar oue, inost description languages that have been developed for cumputatioual morphology (e.g., I KC)- SKENNIEMI841, [G(}RZ881 ) have tended to locus more on the orthographic and of fixation rules, and pay less at- tention to explicitly captaring the regularities within and between parudignts. Recently, some researchers have be- gun exploring the advantages to be derived from a nora. tion in which paradigms play a more central role (e.g., [CALDER891. IRUSSELL911). This paper presents such a notation, called PDL (for Paradigm Description l.au- guage), which we are using as the basis of the morpho- logical an~dyzer for A1-STARS, a multi-lingual "lexicon- assisted" informatiml retrieval system ([ANICK901). It has been a goal of our high-level language design to pre- ~rve, as umch as possible, the kinds of descriptive de- vices traditiorually used in grammar books. Our approach to the …

Content truncated to 500 words