FAILURE ANALYSIS -- When a system fails, it is necessary to determine the
cause of the malfunction in order to restore the system to its functional
capacity. The Fault Tree Diagnosis System (FTDS) from NASA Ames Research
Center is an automated diagnostic system which identifies the likely
causes of a specified failure based upon information represented in system
reliability models called fault trees. A fault tree is a graphical
representation of the logical relationships among the components in a
system. The structure of the tree describes how the system can reach an
undesired state. FTDS is a modified implementation of the failure cause
identification phase of Narayanan and Viswanadhams' methodology for
knowledge acquisition and reasoning in the failure analysis of systems.
This method is based on knowledge bases of if-then rules constructed
directly from a fault tree representation of the system to be diagnosed.
In FTDS, the knowledge base of if-then rules has been replaced with an
object-oriented fault tree representation. This enhancement yields more
efficient failure cause identification and allows dynamic updating of the
knowledge base.

FTDS, ARC-13019, is written in C language, C++, and Common for use on UNIX
workstations. The diagnosis module itself requires Common Lisp with
Flavors extensions and foreign functions extensions. This module can be
run on a variety platforms from a Mac II to a Sun SPARCstation, as long as
LISP environment is available. The two graphical utility programs that
make using the diagnosis module much easier (Displayer and Tree Editor)
require LEX, X11 release 4, Interviews 2.6, and Gnu C++ 1.37. A color
monitor is recommended. The standard distribution medium for FTDS is . _
inch streaming magnetic tape cartridge in UNIX tar format. It is also
available on a 3.5 inch diskette in UNIX tar format. Program $1,750;
documentation $16.

COSMIC, The University of Georgia
382 East Broad St, Athens, GA 30602-4272
706-542-3265  fax: 706-542-4807

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