Flow Constraint Language for Coordination by Exogenous Connectors

Abstract

Construction of Cyber-Physical Systems (CPS) by reusing or composing existing components (sub-systems) is the emerging need in software based system development. For software development, a number of paradigms exists to deal with the reusability at different levels. Component-based development (CBD) represents a paradigm shift in software development for its emphasis on development for/with reuse. Software composition mechanisms are the essence of this paradigm. In general, a software system in CBD is comprised of two kinds of elements: computation and communication. Defining/creating these elements in a generic way and for system construction allowing these elements to be customised in specific to the system needs can increase the level of reusability. In this paper, for a development paradigm (referred to as EX-MAN in CBD) for CPS construction, we focus on software elements dealing with the communications elements (referred to as connectors) among the computational elements. We define constraints (written in our proposed flow constraint language (FCL)) as a property for coordination by the exogenous connectors to customise the behaviour of connectors for system construction. In this paper, the semantics of FCL constraints for a sample exogenous connector is described for system construction/execution. In order to verify the operational semantics of FCL constraints of this exogenous connector, we use Coloured Petri Nets (in CPN tools) to model and simulate the connectors with constraints. Exogenous connectors are implemented in a tool exogenous composition framework (ECF) for system construction.