Using UML Profiles for Sector-Specific Tailoring of Safety Evidence Information

Safety-critical systems are often subject to certification as a way to ensure that the safety risks associated with their use are sufficiently mitigated. A key requirement of certification is the provision of evidence that a system complies with the applicable standards. The way this is typically organized is to have a generic standard that sets forth the general evidence requirements across different industry sectors, and then to have a derived standard that specializes the generic standard according to the needs of a specific industry sector. To demonstrate standards compliance, one therefore needs to precisely specify how the evidence requirements of a sector-specific standard map onto those of the generic parent standard. Unfortunately, little research has been done to date on capturing the relationship between generic and sector-specific standards and a large fraction of the issues arising during certification can be traced to poorly-stated or implicit relationships between a generic standard and its sector-specific interpretation. In this paper, we propose an approach based on UML profiles to systematically capture how the evidence requirements of a generic standard are specialized in a particular domain. To demonstrate our approach, we apply it for tailoring IEC61508 - one of the most established standards for functional safety - to the Petroleum industry.