EXECUTABLE SPECIFICATIONS WITH DATA-FLOW DIAGRAMS

Specifications of information systems applications are often based on the use of entity-relationship (ER) and data-flow diagrams (DFD), whic h cover, respectively, the conceptual modelling of data and funtions. This paper introduces VLP: an executable visual language for formal sp ecifications and prototyping which integrates ER and DFD diagrams in a semantically rigorous and clear way. Unlike existing commercial produ cts (so-called CASE tools), which can support good-quality documentati on, simple forms of consistency checking and bookkeeping, VLP also sup ports executable specifications, which provide a prototype of the desi red application. After reviewing the principles of VLP, the paper outl ines the structure of the ECASET environment in which VLP is embedded. In particular, it shows how the environment supports the stepwise der ivation of specifications, from informal to formal, and how it support s specification-in-the-large.