A graphical representation and prototype editor for the Formal Description Technique Estelle

This paper presents a graphical representation for the Formal Description Technique Estelle, which has up until now been restricted to a textual syntax based on the general programming language Pascal. The graphical syntax and semantics of the representation are fully descriptive of a general Estelle system and complies with the ISO Estelle standard ISO97]. This representation aims to become a standard technique for formally specifying and simultaneously documenting concurrent, communicating systems. Conventions introduced in existing graphical Estelle tools are re-used, as are graphical concepts which have become familiar through widespread use of the similar Speciication and Description Language (SDL). In addition, we present a syntax-directed editor based on the graphical syntax. The editor enables practical application of the graphical technique, by translating a graphical description to the equivalent textual form which can be input into existing Estelle tools. The reverse function makes it possible to view and navigate existing textual Estelle speciications more eeectively.