Modelling Adaptive Systems in ForSyDe 1

Emerging architectures such as partially reconfigurable FPGAs provide a huge potential for adaptivity in the area of embedded systems. Since many system functions are only executed at particular points of time they can share an adaptive component with other system functions, which can significantly reduce the design costs. However, adaptivity adds another dimension of complexity into system design since the system behaviour changes during the course of adaptation. This imposes additional requirements on the design process, in particular system verification. In this paper we illustrate how adaptivity is treated as first-class citizen inside the ForSyDe design framework. ForSyDe is a transformational system design methodology, where an initial abstract system model is refined by the application of semantic-preserving and non-semantic preserving design transformations into a detailed model that can be mapped to an implementation. Since ForSyDe is based on the functional paradigm we can model adaptivity by using functions as signal values, which we use as the base for our concept of adaptive processes. Depending on the level of adaptivity we categorise four classes of adaptive process, spanning from parameter adaptive to interface adaptive process. We illustrate our concepts by two typical examples for adaptivity, where we also show the application of design transformations.