tailieunhanh - Báo cáo khoa học: "FORMALISMS FOR MORPHOGRAPHEMIC "

Recently there has been some interest in rule formaltsms for describing morphologically significant regularities in orthography of words, largely influenced b y the w o r k of Koskenniemi. Varioue implementationa of these rules are possible, but there are some weaknesses in the formalism as it stands. An alternative specification formalism is possible which solves some of the problems. This new formalism can be viewed as a variant of the "pure'" Koskenniemi model w i t h certain conetraints relaxed. The new formalism has particular advantages for multiple cheLracter changes. . | FORMALISMS FOR MORPHOGRAPHEMIC DESCRIPTION Alan Black. Graeme Ritchie. Dept of Artificial Intelligence University of Edinburgh 80 South Bridge Edinburgh EH11HN SCOTLAND Steve Pulman and Graham Russell Computing Laboratory University of Cambridge Com Exchange Street Cambridge CB2 3QG ENGLAND ABSTRACT Recently there has been some interest in rule formalisms for describing morphologically significant regularities in orthography of words largely influenced by the work of Koskenniemi. Various implementations of these rules are possible but there are some weaknesses in the formalism as it stands. An alternative specification formalism is possible which solves some of the problems. This new formalism can be viewed as a variant of the pure Koskenniemi model with certain constraints relaxed. The new formalism has particular advantages for multiple character changes. An interpreter has been implemented for the formalism and a significant subset of English morphogra-phemics has been described but it has yet to be used for describing other languages. Background This paper describes work in a particular area of computational morphology that of morphogra-phemics. Morphographemics is the area dealing with systematic discrepancies between the surface form of words and the symbolic representation of the words in a lexicon. Such differences are typically orthographic changes that occur when basic lexical items are concatenated . when the stem move and suffix ed are concatenated they form moved with the deletion of an e . The work discussed here does not deal with the wider issue of which morphemes can join together. The way we have dealt with that question is described in Russell et al. 1986 . The framework described here is based on the two-level model of morphographemics Koskenniemi 1983 where rules are written to describe the relationships between surface forms . moved and lexical forms . move ed . In his thesis Koskenniemi 1983 presents a formalism for describing .