Abstract
The paper describes experience of a large-scale application of the Z specification language to the formalisation of parts of the transformation and analysis functionality contained in a static analysis toolset for COBOL. Aspects of the development described in the paper are: the combination of 'diagrammatic' analysis and design techniques with formal specification, in order to obtain well-structured and comprehensible specifications; techniques to utilise object-oriented structure in the domain in order to structure a specification; benefits of using formal specifications in an industrial environment in which expertise in formal methods was restricted, and which was predominately within a traditional database and imperative programming culture.