The GTI~syst~m is a tree-to-tree transducer developed for teaching purposes in machine translation. The transducer is a specialized production system giving the linguists the tools for expressing infon~ation in a syntax that is close to theoretical linguistics. Major emphasis was placed on developing a system that is user friendly, uniform and legible. This paper describes the linguistic data structure, the rule formalism and the control facilities that the linguist is provided with.
