JACY is a cooperation project of DFKI and YY Technologies, Mountain View, Ca, USA. It is aimed to develop an open source grammar of Japanese. This grammar will be developed in the formalism of Head-Driven Phrase Structure Grammar (HPSG). HSPG is an integrated syntax-semantic approach on a lexical basis. Complex sign are combined by unification. The Japanese grammar shall have a broad lexical and syntactic coverage, such that it will be possible to use it in products like automatic email response systems. The semantic formalism is Minimal Recursive Semantics (MRS). MRS offers an interface between syntax and semantics using feature structures. The formalism has syntactically flat structures, offers at the same time the possibility of the handling of scope relations. The semantics will be developed in close co-operation with the LinGO English Resource Grammar.