Reasoning about Safety during Software Architecture Design

Architects use a variety of techniques to evaluate designs to determine the degree to which a product produced from the architecture would possess the desired levels of specific quality attributes. Reasoning frameworks are used to guide architecture definition by predicting the extent to which a software architecture satisfies its quality requirements. There has been much research about such direct runtime attributes as performance and modifiability but much less work has been done concerning such indirect attributes as safety. We present a framework for reasoning about safety that is based on the observation that safety hazards sometimes lead to accidents when certain quality requirements of the system are not satisfied. This naturally leads to the use of reasoning frameworks for these other qualities as a means to indirectly reason about safety. We present our technique that utilizes standard safety engineering activities and a risk-based qualitative reasoning approach to make a judgment on the satisfaction of safety requirements by the architecture.