A Modelling Approach for System Life Cycles Assurance

System assurance involves assuring properties of both a target system itself and the system life cycle acting on it. Assurance of the latter seems less understood than the former, due partly to the lack of consensus on what a ‘life cycle model’ is. This paper proposes a formulation of life cycle models that aims to clarify what it means to assure that a life cycle so modelled achieves expected outcomes. Dependent Petri Net life cycle model is a variant of coloured Petri nets with inputs and outputs that interacts and controls the real life cycle being modelled. Tokens held at a place are data representing artefacts together with assurance that they satisfy conditions associated with the place. The ‘propositions as types’ notion is used to represent evidence(proofs) for assurance as data included in tokens. The intended application is a formulation of the DEOS life cycle model with assurance that it achieves open systems dependability, which is standardised as IEC 62853.