Software Requirement Analysis for Safety

Requirements V&V

Software faults that lead to failures differ from hardware as they are not random or the result of wear out. They are designed into the code either through coding errors or because of errors/omissions/ambiguities in software requirements. In safety-critical software, which is rigorously tested, remaining faults are mostly due to requirement issues, and much less so due to coding errors. For this reason V&V of software requirements is at least as crucial as V&V for hardware, if not more so.

Most failures are the result of the code not being designed to deal with certain (mostly rare) events: conditions and inputs. Moreover, it is in the requirements that mitigations for failures are listed. For serious failures, multiple (redundant) mitigation strategies are required. A safety-informed requirements V&V focuses on these types of omissions. 

In order to perform a requirements review that can focus on safety-aspects of the code SoHaR uses the following design products:

1. System architecture

2. Complete system requirements documents

3. System hazard analysis and/or Fault Tree Analysis

 For more information about SoHaR's Software Reliability and Safety program please contact us at becky@sohar.com

Additional reading: Requirements for Handling of Rare Conditions