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Iterative Expansion Region
When the value of iterative is specified for the mode of an expansion region, execution within the region must occur in sequence. An expansion region is a type of activity group that contains one or more actions. These actions are executed multiple times depending on the number of elements in the input collection that arrive at one or more expansion nodes positioned on the edge of the region. The results of the actions may be placed in one or more expansion nodes acting as outputs.
Explanation
An expansion region provides a mechanism to execute one or more actions a number of times. The mode value of iterative implies that executions of the region occur one after the other, and in sequence. The next execution cannot occur until the previous one has been completed. If the executions produce outputs these are placed in the output collection at the end of each execution. The input collection of elements may be ordered and in which case the tokens are presented in order.
Important Points
An expansion region must have one or more expansion nodes as arguments and can have zero or more expansion nodes as outputs.
One or more expansion node inputs provide arguments to the region. An expansion region must have at least one expansion node input. If the region has any outputs these are directed to expansion node outputs, which are the results of the region.
A parallel expansion region is related to an iterative expansion region as they are both types of expansion regions. The value parallel means that the group of actions enclosed within the region can occur in parallel. A value of iterative means that the execution of the actions must occur in sequence, and the next execution cannot occur until the previous one has been completed.
A stream expansion region is related to an iterative expansion region as they are both types of expansion regions. The value of stream means that there is a single execution of the region. A value of iterative means that the execution of the actions must occur in sequence, and the next execution cannot occur until the previous one has been completed.
