Software fault tree analysis services
Ann Marie Neufelder has been constructing software fault trees for 30 years for many different application types.
Software fault trees should be part of an overall system fault tree since software and hardware failures are generally not independent. The SFTA is useful when:
There is a system failure has occurred occurred and it isn't known whether the root cause is due to the hardware, the software or both.
Determining the system failures that can be caused by both the hardware or the software.
Facilitating the SFMEA. The SFTA can be used to establish the consequences section of the SFMEA
The basic software failure events are:
- False alarms
- Insufficient error handling
- Sequencing or order
- Outputs are incorrect
- Outputs are valid but not expected
Common mistakes made when doing software fault trees
- Excluding hardware from the analysis or isolating the software from the rest of the system
- Starting with "software fails" as the top event
- Neglecting to use standard failure events and failure modes checklists during the brainstorming
- Not having the appropriate subject matter experts in the analyses
- Neglecting to add the "shall nots" divulged from the fault trees into the requirements, design documents and test plans
- Neglecting to review past historical failure events
- Performing the analysis too late in development to impact the design