Loops enable the processing of repeating instances of a schema or field name. There are different uses for looping:
A For Each loop is used to iterate through a list of items in a document. Processing continues until all items in the list have been processed.
A User-Defined loop requires the setting of the exit criteria from the loop and the sequence repeats until the exit condition is true.
Iteration can also be modeled using a combination of a join as the entry point and split or rule as the exit point.