The Software Safety Critical Function Analysis: The First Step in Developing Safe Software

摘要

A successful software safety engineering activity is based upon both the hazard analysis process and the software integrity process. Emphasis is placed on the context of the "system" and how software contributes to failures, faults, hazards, and/or mishaps. From the perspective of the system safety engineer and the hazard analysis process, software is considered a subsystem. In most instances, the system safety engineers must perform the hazard analysis process while the software development, software test, and independent verification and validation (IV&V) team(s) implement the software integrity process. The hazard analysis process is an activity that identifies and mitigates the exact software contributors to hazards. The first step in this process is the conduct of the System Safety Critical Function Analysis (SSCFA) which documents the identification and assessment of the safety-critical software functions. The analysis begins by constructing a worksheet to document the analysis of each software function to determine if it safety critical and developing a Software Criticality Matrix used in the analysis of each software function. Each function that was determined to be safety critical was further analyzed and assigned a Software Criticality Index (SCI) and a RTCA/DO-178B Software Level. The paper explains this process through example.