The Role of Reversible Grammars in Translating Between Representation Languages

A capability for translating between representation languages is critical for effective knowledge base reuse. We describe a translation technology for knowledge representation languages based on the use of an interlingua for communicating knowledge. The interlingua-based translation process can be thought of as consisting of three major steps: (1) translation from the source language into a subset of the interlingua, (2) translation between subsets of the interlingua, and (3) translation from a subset of the interlingua into the target language. The first translation step into the interlingua can typically be specified in the form of a grammar that describes how each top-level form in the source language translates into the interlingua. We observe that in cases where the source language does not have a declarative semantics, such a grammar is also a specification of a declarative semantics for the language. We describe the conditions under which such a grammar is reversible so that the grammar can also be used to translate out of the interlingua. In particular, we formally describe the translation process into and out of an interlingua, present a method for determining whether a given grammar in fact specifies how to construct a translation for every top-level form in a given source language; and present a method for determining whether a given grammar is reversible so that it can be used to translate both into and out of an interlingua.