Independence and Non-interference: Two Cardinal Concepts to Develop EE Architectures Hosting Safety-Critical Systems

The EASIS project clarified typology of dependent failures (Common Cause Failures, Common Mode Failures and Cascading Failures). Typology of dependent failures is a key concept used within safety standards such as IEC61508, or the on-going ISO26262. A presentation of this typology supported with concrete examples will be used to introduce a discussion on dependent failure analysis and bring in the distinction between the concepts of independence and absence of interference. Independence of EE architectural elements is required particularly between two architectural elements implementing a function and its associated safety mechanism. Absence of interference which is less demanding than independence is required to allow architectural elements of different criticality to cohabit (among others, safety-related elements and non-safety-related elements). Typical EE automotive examples will support this discussion