The purpose of the Fault Tree Analysis view is to support viewing and editing of so-called Fault Trees, used in Fault Tree Analysis (FTA). The view can be configured to suit specific meta models and needs. This article introduces an FTA meta model and covers how to configure the Fault Tree Analysis view as well as how to incorporate fault trees in reports for printing.
- Configuring the View
- Including Fault Tree Graphs in Reports
- Including Fault Tree Minimal Cut Set in Reports
- A Fault Tree Analysis meta model
- An installation of the SystemWeaver Explorer client (swExplorer)
- The SystemWeaver SWExtension.FaultTreeGraph extension is located in the Client's swExplorerExtensions directory
- Assignment of the SW Architect role in the server
Example FTA Meta Model
Below is a basic SystemWeaver meta model used to demonstrate the Fault Tree Analysis solution.
|2CEU||Fault Tree Analysis||The Fault Tree Analysis container item, i.e., the top-level item in the structure.|
|2CET||Fault Event||A failure or error in a system component or element. They can be root or intermediate.|
|2CEV||External Event||An event that is normal and guaranteed or expected to occur. They are not considered to be faults, but still contribute to the generation of faults.|
|2CLD||Logic AND||An AND gate that interconnects contributory events and conditions in the fault tree. The output occurs only if all inputs occur (inputs are independent).|
|2CLO||Logic OR||An OR gate that interconnects contributory events and conditions in the fault tree. The output occurs if any input occurs.|
Configuring the View
<ContainerItem sid="2CEU" />
<LeafItem sid="2CET" />
<ExternalEventItem sid="2CEV" />
<AndItem sid="2CLD" />
<OrItem sid="2CLO" />
<RootNodePart sid="2IFW" />
<LogicInputPart sid="2IFI" />
<TimeScaleAttribute sid="FRTS" />
<ProbabilityAttribute sid="FTAR" />
<TransferLabelAttribute sid="TRAN" />
The ContainerItem sid attribute defines the item type of the top item ("Container item") in a Fault Tree Analysis model.
The RootNodePart sid attribute defines the part type of the root fault under the Container Item.
The LeafItem sid attribute defines the item type of a fault event.
The optional ExternalEventItem element specifies the item type used for the External Event items*.
The AndItem sid attribute defines the item type of an And gate in the Fault Tree Analysis model.
The OrItem sid attribute defines the item type of an Or gate in the Fault Tree Analysis model.
The LogicInputPart sid attribute the part type used for a sub tree item in the fault tree. Note that since this is a common part for the And and Or gates these need to be sub types of a common (abstract) gate type.
The IntermediateNodeDefinitionAttribute sid attribute defines an attribute type that can be used for the definition of the "intermediate event" symbol in the fault tree, used only for events: the intermediate event of logic gates is defined as the name of the gate. The attribute is a part attribute on the LogicInputPart where the DefType is an event.
The TimeScaleAttribute sid attribute defines the alternative time scales assumed for the ProbabilityAttribute value.
Note: This value is used by the Grid sub view, and that view only accepts a single common value used for all events within a single fault tree.
The ProbabilityAttribute sid attribute defines a numerical (integer, float) attribute type that represents the probability of an event (expressed at the time scale of the TimeScaleAttribute attribute).
The optional TransferLabelAttribute attribute specifies an item attribute to be used as a label for transfer in and transfer out symbols in a report where the FaultTreeGraph tag is used.
* External events represents events that are not considered as being faults, but still contributes to the propagation of faults.
Including Fault Tree Graphs in Reports
Reports can be configured to include fault trees using the extension-specific tag "SWExtension.FaultTreeGraph".
<Extension name="SWExtension.FaultTreeGraph" maxTreeHeight="" transferOut=""/>
The optional attribute maxTreeHeight controls the depth of the produced tree. Any truncated tree branches will be indicated by so-called transfer in symbols. This option is useful when working with very large graphs.
The optional attribute transferOut indicates a transfer/continuation of one fault tree to another. The allowed values are true/False.
<Report> <Extension name="SWExtension.FaultTreeGraph" maxTreeHeight="2" transferOut="false"/> <!-- do nothing special since this level is covered in tree graph--> <ForEach select="/2IFW/2IFI/2IFI[SID!='2CET']"> <ApplyTemplate name="SubTree"/> </ForEach> <Template name="SubTree"> <Extension name="SWExtension.FaultTreeGraph" maxTreeHeight="2" transferOut="true"/> <!-- do nothing special since this level is covered in tree graph--> <ForEach select="/2IFI/2IFI[SID!='2CET']"> <ApplyTemplate name="SubTree"/> </ForEach> </Template> </Report>
The fault tree graph of the selected fault tree item is produced:
Including Fault Tree Minimal Cut Set in Reports
Reports can be configured to include FTA minimal cut sets using the extension-specific tag "MinimalCutSet".
<Report> <ForEach select="/IRSI"> <ApplyItemTemplates /> </ForEach> <ItemTemplate type="2CEU"> <Log>ItemTemplate for FaultTree</Log> <Description/> <Extension name="MinimalCutSet"/> </ItemTemplate> </Report>
Learn more about how to interact with the view in the swExplorer client.
There is also an example graph as an alternative to using the FaultTreeGraph extension.