Basically a subworkflow is an ordinary workflow started by the task <ForkSubprocess> within another workflow. A single <ForkSubprocess> task can start one or multiple subprocesses at once. Note, that the terms subworkflow and subprocess are used interchangeably here.

The name of the process to start can be specified either statically in the subprocess attribute or dynamically as variable in the subprocessVariable attribute. It is also possible to start multiple subprocesses in one step, either by specifying an aggregation variable containing multiple subprocess names or by iterating over an aggregation variable containing data elements, starting one subprocess per element. See ForkSubprocess for the full attribute reference.

Subprocesses are always started as separate processes while the main process continues. There are two different modes in which subprocesses may be started:

The <Parameters> child element supports two assignment mechanisms: <Assign> transfers a single value into a subprocess variable, while <AssignStruct> assigns multiple values from a Struct XML. When starting multiple subprocesses, parameter assignments may refer to the current iteration element or index to pass different values to each subprocess. See Parameters for details.