Fault tree and digraph models are frequently used for system failure
analysis. Both type of models represent a failure space view of the system
using AND and OR nodes in a directed graph structure. Fault trees must
have a tree structure and do not allow cycles or loops in the graph.
Digraphs allow any pattern of interconnection between loops in the
graphs.

A common operation performed on digraph and fault tree models is the
calculation of minimal cut sets. A cut set is a set of basic failures that
could cause a given target failure event to occur. A minimal cut set for a
target event node in a fault tree or digraph is any cut set for the node
with the property that if any one of the failures in the set is removed,
the occurrence of the other failures in the set will not cause the target
failure event. CUTSETS, from NASA Ames Research Center, will identify all
the minimal cut sets for a given node. The CUTSETS package contains
programs that solve for minimal cut sets of fault trees and digraphs using
object-oriented programming techniques. These cut set codes can be used to
solve graph models for reliability analysis and identify potential single
point failures in a modeled system. CUTSETS includes a utility program
that will convert the popular COD format digraph model description files
into text input files suitable for use with the CUTSETS programs.

CUTSETS, ARC-13286, is written in C-language to be machine independent. It
has been successfully implemented on a Sun running SunOS, a DECstation
running ULTRIX, a Macintosh running System 7, and a DEC VAX running VMS.
The RAM requirement varies with the size of the models. An electronic copy
of the documentation in Macintosh Microsoft Word format is included on the
distribution medium. Program $300; documentation $14.

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

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