| DPL FAULT TREE |
adds the ability to build and analyze fault trees to DPL's powerful evaluation engine. You
can build fault trees as standalone models, or combine them with influence diagrams, decision
trees and spreadsheets.
Fault Tree Modelling
A fault tree is a structured model used to analyze the risk in a system. A fault tree
enumerates the system components liable to failure, and expresses how each contributes
to the robustness of the system. Fault trees are used in numerous applications including analyzing
the safety of nuclear power plants,
the reliability of launch vehicles and the security of computer networks.
DPL Fault Tree provides a rich set of operators:
Basic events
AND gates (any number of inputs)
OR gates (any number of inputs)
NOT gates (to build noncoherent fault trees)
Value nodes for probabilities and costs
Dependent events
Embedded modules (subtree libraries)
Building a fault tree in DPL is easy. Start with the top event, connect gates and binary events below,
and lastly assign probabilities to the basic events at the bottom. DPL has time-saving features for
creating multiple events and establishing connections. You can be running an analysis in minutes!
For more advanced modelling, DPL helps you build up complex fault tree structures from simple modules.
DPL's fault tree modules act like custom gates, and you can include as many as you like in your
fault tree. You can even create libraries of common modules in separate project files, so they can
be shared among the members of a workgroup.
Circuit Diagrams
A circuit diagram is an alternative way of looking at the structure of a fault tree. The system
will fail if the "circuit" is broken -- that is, if all the lines from the "power source" on the right
to the "light bulb" on the left are cut. A circuit diagram provides a graphical view of the
qualitative aspects of the system, such as redundancies and single points of failure.
In DPL, you can switch between the tree and circuit diagram views of a fault tree at the press of a button.
Minimal Cut Sets
The central fault tree analysis is the calculation of the minimal cut sets. A cut
set is a list of component failures that would result in system failure; it is minimal
if it doesn't contain any unnecessary failures. DPL Fault Tree has a fast, proprietary
algorithm for calculating minimal cut sets. Once calculated, the minimal cut sets can be displayed
in tabular or circuit diagram format.
However you view them, you'll be able to see both the probability of occurence and the
cost of each cut set. In a security context, sorting the cut sets by cost allows you to focus on the
"cheapest" failure points, that is, the ways an adversary could most easily attack the system.
Partial Derivatives
A fault tree is a mathematical function which takes a set of basic events as inputs and gives
the probability of failure as output. The partial derivatives of this function with respect to each of
its inputs give a useful comparative sensitivity analysis specific to fault trees. An event's probability
and its partial derivative give its maximum impact on the likelihood of
system failure. Efforts to improve the robustness of the system should be focused on high-impact events.
DPL provides the automated ability to calculate and graphically display the partial derivatives of the fault tree.
Other Key Features
- All of the power and features of DPL Professional
- Aggregation of multiple expert opinions
- Module embedding (in influence diagrams or other fault trees)
- Time series fractiles
- Maximum impact (combines partial derivatives with probabilities)
- Object linking and embedding of documentation from other applications
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DPL Professional features
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