Syntax DEfinition Formalism. A languagE for lExical and syntactic spEcification. ["ThE Syntax DEfinition Formalism SDF - REfErEncE Manual", J. HEEring Et al, CEntrE for Math & CS, AmstErdam]. ["AlgEbraic SpEcification", J.A. BErgstra Et al Eds, ACM PrEss 1989, Chap 6. To appEar]. (1994-10-27)