Dynamic Data Management in STEP

The ISO 10303 (STEP) is a set of standards concerning all the aspects of product data exchange and sharing and it is now widely accepted in the industrial environments. In par1icular STEP provides the language EXPRESS which is a powerful formalism for data description, mainly used to develop the well known Application Protocols, such as the AP 214 which is specifically tailored for the automotive environment. EXPRESS allows to describe data in a static way only, without providing mechanisms useful to modelling the evolution and interactions of data. To overcome this drawback and to give behavioural features to EXPRESS dala descriptions, some extensions to EXPRESS have appeared in the literature. The solution proposed in this paper is based on a different approach. In fact we will show how behavioural features can be added to EXPRESS by integrating that language with LOTOS that is a well-estab1ished and powerful formalism standardised by ISO to describe concurrent and distributed systems. The resulting new language, that we called EXPRESS-LOTOS, allows us to use EXPRESS data descriptions as the data part of LOTOS specifications as they are, without any modification. The advantages arising from such an integration are illustrated by means of a simple example based on a small fragment of the AP 214 application protocol.