Types of SWHA Techniques

Within the SWHA arena, a number of techniques have gained increasing popularity as automated system complexity progresses. Each type of SWHA has its use during the various phases of a product s life cycle, as described here. 

The Software Preliminary Hazard Analysis Used to identify software program routines that are considered to be safety critical, this analysis is conducted prior to software program coding. To perform the analysis, the analyst should make reference to any available system specifications, interface documentation, functional flow diagrams, software flow charts, storage and file allocation specifications, and any other program descriptive information. 

As a first-step evaluation of large, software intensive systems, it has the added advantage of providing for the separation of software interfaces into safety critical and safety noncritical functions which greatly facilitates the overall analysis effort. Obviously, proper performance of a software analysis in the preliminary stages will also reduce the potential cost of any subsequent analyses. 

The major disadvantage is that, at the preliminary level, the analysis is not a structured technique it is somewhat limited to only high level functions and, thus, additional analyses of complex systems are often required, especially where safety critical software functions have been identified. 

Software Fault Hazard Analysis Similar in concept and structure to the system hazard analysis (SHA) which is conducted on system hardware, the software fault hazard analysis will analyze and evaluate a computer software program to identify critical areas in the programming which may contribute to or directly cause a hazard risk. Such risks may be due to an undetected hardware failure or incorrect inputs into the operation of the system software. The software FHA will also attempt to uncover any probable errors that can possibly develop in the software after system activation. 

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