LoopNode: basic running example | Webel IT Australia

The notorious LoopNode is likely one of the least used and least popular offerings in UML, but it can be made to run, which is not to say it's the easiest way to achieve an executable loop. (In a later slide page there is a mini video of a LoopNode actually running using a loopVariable.)

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Modelling and style

UML-2.5.1: 'When an ExecutableNode completes an execution, the control token representing that execution is removed from the ExecutableNode and control tokens are offered on all outgoing ControlFlows of the ExecutableNode. That is, there is an implicit fork ...'

All of which achieves something like:


for (int i = 1; i < 5; i = i *2) {
//do stuff
}

Or use UML-friendly Action Language for Foundational UML (Alf); because not every single low-level aspect of UML is a good fit for graphical modelling.

And remember, you can always just use ControlFlows and/or ObjectFlows with DecisionNode and MergeNode to create a "manual" loop:

Loop: running example using DecisionNode and MergeNode and an Integer property in a context

Visit also: TIP/GOTCHA: SysMLv1/fUML: Cameo Simulation Toolkit: If you have a ControlFlow loop with a DecisionNode test you MUST have a MergeNode for the continuation path ControlFlow (typically entered also from an InitialNode or other loop starting point).

Visit also: TIP/GOTCHA: SysMLv1/UML: Cameo Simulation Toolkit: If you use a «decisionInputFlow» to a DecisionNode you MUST also have a ControlFlow to the DecisionNode; if you don't use an explicit «decisionInputFlow» you don't need the "extra" ControlFlow

Visit also: TIP: SysMLv1/UML: Cameo Simulation Toolkit: HOWTO convert an fUML ReadLine CLI String to a Boolean for cleaner DecisionNode tests against a LiteralBoolean [true] guard.

Up next

LoopNode with loopVariable - ADVANCED REFERENCE

Notes

[CAVEAT] Cameo Simulation Toolkit 19SP3 DOES NOT support 'setupPart' in LoopNode (because fUML does not)

[TIP]{OPTION} Not every task in Activity Diagrams is well-suited to graphical modelling and LoopNode and ConditionalNode are notoriously fiddly to setup; consider using Action Language Helper (ALH) or Action Language for Foundational UML (Alf)

[ISSUE] UML-2.5.1 refers to 'isTestFirst' in 16.11.3.4 but to isTestedFirst in the attributes list for LoopNode under 16.14.30.4 Attributes

Snippets (quotes/extracts)