ZML: Z Formal Specifications Using XML

This paper describes a project, the purpose of which was to determine the feasibility of using XML as a vehicle for carrying the contextual meaning of a Z formal specification. This paper describes a definition of the popular Z (pronounced z G), formal specification language, in terms of an eXtensible Markup Language (XML) Data Type Definition (DTD). Using the Sun JAXB tool, we wrote a Java program that supports building and processing a tree structure based on the DTD. Using that DTD, a small Z specification was rendered in XML. We then present a case study Java program written to demonstrate the ability to examine and process the Z specification as an internal tree structure. Finally, we describe some limitations encountered in the JAXB tool and suggestions for improving it. With the feasibility proven, we could then go on to use the XML vehicle to pass the Z specification to a theorem prover, a code generator, or other, as yet unforeseen tools. Z is a formal specification language, used for specifying requirements or designs, and to which formal proofs of correctness and completeness can be applied. XML allows us to define a Z schema, so it can be used with other software tools to contextually render the schema. We describe a complete Data Type Definition (DTD), denoted ZML, for the general Z schema format. While pursuing our primary purpose, we have found some limitations in JAXB, which we describe in this paper.