Program Synthesis from Formal Requirements Speciications Using Apts

Formal speciications of software systems are extremely useful because they can be rigorously analyzed, veriied, and validated, giving high conndence that the speciication captures the desired behavior. To transfer this conndence to the actual source code implementation, a formal link is needed between the speciication and the implementation. Generating the implementation directly from the speciica-tion provides one such link. A program transformation system such as Paige's APTS can be useful in developing a source code generator. This paper describes a case study in which APTS was used to produce code generators that construct C source code from a requirements speciication in the SCR (Software Cost Reduction) tabular notation. In the study, two diierent code generation strategies were explored. The rst strategy uses rewrite rules to transform the parse tree of an SCR speciication into a parse tree for the corresponding C code. The second strategy associates a relation with each node of the speciication parse tree. Each member of this relation acts as an attribute, holding the C code corresponding to the tree at the associated node; the root of the tree has the entire C program as its member of the relation. This paper describes the two code generators supported by APTS, how each was used to synthesize code for two example SCR requirements speciications, and what was learned about APTS from these implementations.