Fault tree analysis for software design

We present a study on software fault tree analysis (SFTA) conducted at the Software Assurance Technology Center at NASA Goddard Space Flight Center. While researchers have made various attempts at SFTA, software assurance practitioners have been slow to adopt it. One reason is the intense manual effort needed to identify and draw the fault trees for the code of large software projects. Another is the lack of commercial tools to assist in the technique for software. Most SFTA research efforts have been directed at requirements or code. Performing SFTA on the design may enable application of SFTA to critical code only, thus reducing the amount of effort. We attempt to develop a relationship between UML™ design diagrams and fault tree symbology to enable adaptation of a commercial FTA tool to at least one software design language. Such a result would reduce the amount of fault tree effort both for size (design instead of code) and for manual effort.