A Morphographemic Model for Error Correction in Nonconcatenative Strings.pdf

a r X i v : c m p - l g / 9 5 0 4 0 2 4 v 2 2 8 A p r 1 9 9 5 A Morphographemic Model for Error Correction in Nonconcatenative Strings Tanya Bowden ? and George Anton Kiraz ? University of Cambridge Computer Laboratory Pembroke Street, Cambridge CB2 3QG {Tanya.Bowden, George.Kiraz}@cl.cam.ac.uk http://www.cl.cam.ac.uk/users/{tgb1000, gk105} Abstract This paper introduces a spelling correction system which integrates seamlessly with morphological analysis using a multi-tape formalism. Handling of various Semitic er- ror problems is illustrated, with reference to Arabic and Syriac examples. The model handles errors vocalisation, diacritics, pho- netic syncopation and morphographemic idiosyncrasies, in addition to Damerau er- rors. A complementary correction strategy for morphologically sound but morphosyn- tactically ill-formed words is outlined. 1 Introduction Semitic is known amongst computational linguists, in particular computational morphologists, for its highly inflexional morphology. Its root-and-pattern phenomenon not only poses difficulties for a mor- phological system, but also makes error detection a difficult task. This paper aims at presenting a morphographemic model which can cope with both issues. The following convention has been adopted. Mor- phemes are represented in braces, { }, surface (phonological) forms in solidi, / /, and orthographic strings in acute brackets, 〈 〉. In examples of gram- mars, variables begin with a capital letter. Cs de- note consonants, Vs denote vowels and a bar denotes complement. An asterisk, *, indicates ill-formed strings. The difficulties in morphological analysis and er- ror detection in Semitic arise from the following facts: ? Supported by a British Telecom Scholarship, ad- ministered by the Cambridge Commonwealth Trust in conjunction with the Foreign and Commonwealth Office. ? Supported by a Benefactor Studentship from St John’s College. ? Non-Linearity A Semitic stem consists of a root and a vowel melody, arran