The LOOP step takes as input an array variable that is in the pipeline. It loops over the members of an input array, executing its child steps each time through the loop. For example, if you have a service that takes a string as input and a string list in the pipeline, use the LOOP step to invoke the service one time for each string in the string list.

You identify a single array variable to use as input when you set the properties for the LOOP step. You can also designate a single variable for output. The LOOP step collects an output value each time it runs through the loop and creates an output array that contains the collected output values. If you want to collect more than one variable, specify a document that contains the fields you want to collect for the output variable.