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Foundation ::
Failure Analysis ::
FEAT
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FEAT
Failure Environment Analysis Tool
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SOURCE CODE AVAILABLE
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The Failure Environment Analysis Tool, FEAT, enables people to see and better understand the effects of failures in a system. FEAT uses digraph models to determine what will happen to a system if a set of failure events occurs and to identify the possible causes of a selected set of failures. Failures can be user-selected from either engineering schematic or digraph model graphics, and the effects or potential causes of the failures will be color highlighted on the same schematic or model graphic.
As a design tool, FEAT helps design reviewers understand exactly what redundancies have been built into a system and where weaknesses need to be protected or designed out. A properly developed digraph will reflect how a system functionally degrades as failures accumulate. FEAT is also useful in operations, where it can help identify causes of failures after they occur. Finally, FEAT is valuable both in conceptual development and as a training aid, since digraphs can identify weaknesses in scenarios as well as hardware.
Digraph model
Digraphs models for use with FEAT are generally built with the Digraph Editor, a Macintosh-based application which is distributed with FEAT. The Digraph Editor was developed specifically with the needs of FEAT users in mind and offers several time-saving features. It includes an icon toolbox of components required in a digraph model and a menu of functions for manipulating these components. It also offers FEAT users a convenient way to attach a formatted textual description to each digraph node. FEAT needs these node descriptions in order to recognize nodes and propagate failures within the digraph.
Modelling tables
FEAT users store their node descriptions in modelling tables using any word processing or spreadsheet package capable of saving data to an ASCII text file. From within the Digraph Editor they can then interactively attach a properly formatted textual description to each node in a digraph. Once descriptions are attached to them, a selected set of nodes can be saved as a library file which represents a generic digraph structure for a class of components. The Generate Model feature can then use library files to generate digraphs for every component listed in the modeling tables, and these individual digraph files can be used in a variety of ways to speed generation of complete digraph models.
Preprocessing
FEAT contains a preprocessor which performs transitive closure on the digraph. This multi-step algorithm builds a series of phantom bridges, or gates, that allow accurate bi-directional processing of digraphs. This preprocessing can be time-consuming, but once preprocessing is complete, queries can be answered and displayed within seconds. A UNIX X-Windows port of version 3.5 of FEAT, XFEAT, is also available to speed the processing of digraph models created on the Macintosh. FEAT v3.6, which is only available for the Macintosh, has some report generation capabilities which are not available in XFEAT.
For very large integrated systems, FEAT can be a real cost saver in terms of design evaluation, training, and knowledge capture. The capability of loading multiple digraphs and schematics into FEAT allows modelers to build smaller, more focused digraphs. Typically, each digraph file will represent only a portion of a larger failure scenario. FEAT will combine these files and digraphs from other modelers to form a continuous mathematical model of the system's failure logic. Since multiple digraphs can be cumbersome to use, FEAT ties propagation results to schematic drawings produced using MacDraw II (v1.1v2 or later) or MacDraw Pro. This makes it easier to identify single and double point failures that may have to cross several system boundaries and multiple engineering disciplines before creating a hazardous condition.
FEAT carries the NASA case numbers MSC-21873 (Macintosh version) and MSC-22446 (UNIX version). FEAT was originally released as part of the COSMIC collection.
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