Modelling of a Safety Instrumented System by a Biologically Inspired Modular Construct

We present an ongoing research aimed at investigating aspects of a modelling paradigm where system behaviour is modelled by biologically-inspired, concurrent and autonomous modules through a state based formalism. Such modules are named holons after the work of Arthur Koestler, since they are designed in order to host both the features of parts and wholes. Current modelling paradigms tend at emphasising the parts, but miss the notion of whole. A whole models the associative behaviour observed in the domain of interest, while the parts model the behaviour of a specific entity. Holons are aimed at filling the gap. Holons can act as parts by exhibiting the interface of the state behaviour. At the same time holons can act as wholes, by having the state machine behaviour annotated with actions and triggers which allow them to communicate with other holons, coordinating them and therefore modelling the related associative behaviour. In the paradigm, the two roles are tied together, the associative behaviour becoming recursively the behaviour of a single entity which can be composed into further wholes.