webMethods 10.2 | Service Development Help | Building Flow Services | What Is a Flow Service? | What Is a Flow Step?
 
What Is a Flow Step?
A flow service contains flow steps. A flow step is a basic unit of work (expressed in the webMethods flow language) that webMethods Integration Server interprets and executes at run time. The webMethods flow language provides flow steps that invoke services and flow steps that let you edit data in the pipeline.
webMethods flow language also provides a set of control steps that allow you to direct the execution of a flow service at run time. The control steps allow you to:
*Conditionally execute a specified sequence based on a field value.
*Retry a specified sequence until it succeeds.
*Repeat a specified sequence (loop) for each element in an array field.
In the following flow service, control steps have been inserted to loop through a subset of the flow service and branch to one of two services in the last step of the loop.
Control steps are used to direct the execution of a flow
A flow service can contain the following types of flow steps:
Invocation Steps
INVOKE
Executes a specified service. For more information about this step, see The INVOKE Step.
Data-Handling Steps
MAP
Performs specified editing operations on the pipeline (such as mapping variables in the pipeline, adding variables to the pipeline, and dropping variables from the pipeline). For more information about this step, see The MAP Step.
Control Steps
BRANCH
Executes a specified flow step based on the value of a specified variable in the pipeline. For more information about this step, see The BRANCH Step.
LOOP
Executes a set of flow steps once for each element in a specified array. For more information about this step, see The LOOP Step.
REPEAT
Re-executes a set of flow steps up to a specified number of times based on the successful or non-successful completion of the set. For more information about this step, see The REPEAT Step.
SEQUENCE
Groups a set of flow steps into a series. The SEQUENCE step is implicit in most flow services (that is, the steps in a flow service are treated as a series). However, at times it is necessary to explicitly group a subset of flow steps using SEQUENCE so that they can be treated as a unit. For more information about this flow step, see The SEQUENCE Step.
EXIT
Controls the execution of a flow step (for example, abort an entire flow service from within a series of deeply nested steps, throw an exception without writing a Java service, or exit a LOOP or REPEAT without throwing an exception). For more information about this step, see The EXIT Step.
webMethods Flow Steps
Inserting Flow Steps

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