Integrating AORTA with model-based data specification languages

Abstract

Abstract. AORTA has been proposed as an implementable real-time algebra for concurrent systems where event times, rather than values of data, are critical. In this paper we discuss an extension to AORTA to include a formal data model, allowing integration with a variety of modelbased data specification languages. An example is given using VDM with AORTA to define a time-critical system with important data attributes, and supporting software tools for AORTA and a simple imperative language are described. IntroductionAlthough many timed formalisms exist, AORTA [6] (Application-Oriented RealTime Algebra) is one of the few to consider how designs/specifications of concurrent systems can be implemented in a way that time behaviour can be guaranteed. Supporting tools exist which allow AORTA designs to be simulated, formally verified, and code to be generated [8]. One of the ideas behind the development of AORTA has been that formal methods are good for more than just proof: an unambiguously defined semantics allows early exercising of designs by simulation, and provides a basis for reliable code generation. Whilst proof remains an important aspect of any formal technique, we argue that it is not only the presentation of sound and complete proof theories or automatic verification algorithms which should influence the design of languages, but also the provision of facilities such as code generation and simulation. AORTA only models formally the order and timing of events, and does not deal with data. Implementation details such as values to be passed during communication and the data transformations to be carried out during a given piece of computation are given as annotations to the AORTA design, in the form of fragments of C [5]. In this paper we examine the problem of introducing formal models of data into AORTA designs, and how this affects the notation, the semantics, the tool support and the development method. The approach given here is different from some other proposals [13, 20,23,25], in that rather than integrating with a particular formal specification language, integration within a relatively general framework (described in section 3) is suggested, which allows