Partial substitution yields a subtype. Many systems are known by various names. The names used in EDIS were chosen with the following criteria in mind. In a sense, the names used in EDIS are dummies , since they could be systematically replaced without affecting the global structure. Specifications Specifications of systems are given in several ways for two reasons.
Some specifications can even be copied and pasted directly into a tool, without translation.
Currently, the choice of formalisms is heavily influenced by this editor's preferences. Also the order in which the formalisms appear is based on personal taste. The connection diagram and state graph are shown first, because they are visually oriented. The informal specification describes both the external structure and the observable behavior of the system. The terminology is chosen to be uniform and fairly precise, without being pedantic.