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Foundation ::
Reliability Analysis ::
GO
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GO
Graphics Oriented Program
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Moderators:
Adopt This Application!
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SOURCE CODE AVAILABLE
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The Graphics Oriented program, GO, is one component of Langley Research
Center's HiRel tool system for reliability/availability prediction. GO
provides an interactive, graphical interface for producing input to HARP
(Hybrid Automated Reliability Predictor), the modeling engine at the core of
HiRel.
Often a reliability engineer must graphically represent a reliability model
before it can be solved. GO's graphical input capabilities increase
productivity and decrease the incidence of error. In addition to aiding in
the verification of the reliability model, GO provides reliability engineers
with a readily understandable format for presenting complex model
information to company management, regulatory agencies, and company
customers.
With GO, a user can interactively describe a reliability system
in two notations, either as a fault tree or as a Markov chain. Fault tree
representations are easily described, and HARP can convert them into Markov
chain systems before solving them. Fault trees are readily understandable as
initial models for a reliability system; however, they are unable to model
systems with repair, so the Markov chain conversion can be used thereafter
to complete the model by adding repair transitions and rates.
GUI tools and primitives provided by GO to model Markov chains include the
following: circles to represent a system state or node, arrows to connect
two states in a Markov chain, and arcs for state transitions or repairable
systems. GO also includes many flexible tools and graphical primitives for
modeling fault trees. A failure-box is used to represent system failure.
Circles are provided for basic failure events in a tree. For logical
operations, OR gates, AND gates, and M/N gates (at least M out of N events
must occur in order for this gate to output) are provided.
GO also supplies a number of more complex logical gates. The introduction of
dependency gates in fault tree notation allows the modeling of very large
fault tolerant systems models using a concise, visually recognizable and
familiar graphical language. Functional dependency gates, which take one
"trigger" input and have one or more dependent outputs and a normal output,
can be used in fault tree diagrams. When the trigger event occurs, the
dependent events are forced to occur, while the normal output reflects the
status of the trigger event. The introduction of dependency gates in fault
tree notation allows the modeling of very large fault tolerant systems
models using a concise, visually recognizable and familiar graphical
language. Priority-AND gates are also available when designing fault trees.
In a priority-AND gate, both input events must occur, and the events must
occur in a certain order. Finally, GO includes a cold-spares gate that
produces output when all of the inputs have occurred.
GO carries the NASA case number LAR-15195. It was originally released as part of the NASA COSMIC collection.
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