Designing spelling correctors for inflected languages using lexical transducers

This paper describes the components used in the design of the commercial X u x e n I I spelling checker/corrector for Basque. It is a new version of the Xuxen spelling corrector (Aduriz et al., 97) which uses lexical transducers to improve the process. A very important new feature is the use of user dictionaries whose entries can recognise both the original and inflected forms. In languages with a high level of inflection such as Basque spelling checking cannot be resolved without adequate treatment of words from a morphological standpoint. In addition to this, the morphological treatment has other important features: coverage, reusability of tools, orthogonality and security. The tool is based in lexical transducers and is built using the fst library of Inxight 1. A lexical transducer (Karttunen, 94) is a finite-state automaton that maps inflected surface forms to lexical forms, and can be seen as an evolution of twolevel morphology (Koskenniemi, 83) where the use of diacritics and homographs can be avoided and the intersection and composition of transducers is possible. In addition, the process is very fast and the transducer for the whole morphological description can be compacted in less than 1Mbyte. The design of the spelling corrector consists of four main modules: