Shallow-transfer machine translation engine An open-source shallow-transfer machine translation engine, Apertium is initially aimed at related-language pairs. It uses finite-state transducers for lexical processing, hidden Markov models for part-of-speech tagging, and finite-state based chunking for structural transfer. The system is largely based upon systems already developed by the Transducens group at the Universitat d'Alacant, such as interNOSTRUM (Spanish-Catalan, http://www.internostrum.com/welcome.php) and Traductor Universia (Spanish-Portuguese, http://traductor.universia.net). It will be possible to use Apertium to build machine translation systems for a variety of related-language pairs simply providing the linguistic data needed in the right format.