Invocation StepsINVOKE Executes a specified service.Data-Handling StepsMAP Performs specified editing operations on the pipeline (such as mapping variables in the pipeline, adding variables to theA BRANCH step selects a specified flow step for execution A LOOP step repeats a setof flow stepsWhat Is the Pipeline?The pipeline is the general term used to refer to the data structure in which input andoutput values are maintained for a flow service. It allows services in the flow to sharedata.The pipeline starts with the input to the flow service and collects inputs and outputs fromsubsequent services in the flow. When a service in the flow executes, it has access to alldata in the pipeline at that point.LOOP Executes a set of flow steps once for each element in aspecified array.REPEAT Reexecutes a set of flow steps up to a specified number oftimes based on the successful or nonsuccessful completion ofthe set.SEQUENCE Groups a set of flow steps into a series. The SEQUENCE step isimplicit in most flow services (that is, the steps in a flowservice are treated as a series). However, at times it isnecessary to explicitly group a subset of flow steps usingSEQUENCE so that they can be treated as a unit. EXIT Controls the execution of a flow step (for example, abort anentire flow service from within a series of deeply nested steps,throw an exception without writing a Java service, or exit aLOOP or REPEAT without throwing an exception).

What Is a Flow Step?A flow step is the basic unit of work that instructs webMethods Integration Server aboutwhat to do with data at each stage of a flow service. Flow steps can invoke services anddirect the course of execution. Using flow steps you can: Invoke a service, such as a flow service, Java service, C service, or Web serviceconnector (INVOKE). Conditionally execute one step from a set of specified alternatives (BRANCH). Repeat a set of flow steps up to a specified number of times or until a step in the setfails or succeeds as specified (REPEAT). Group a set of flow steps and control the way in which the failure of a member of theset is processed (SEQUENCE). Repeat a set of flow steps over the elements of a specified array (LOOP). Exit the entire flow or exit a single flow step (EXIT). Link, add, edit, and delete pipeline variables or invoke several services that operateon the same set of pipeline variables (MAP).Inserting and Moving Flow StepsTo insert flow steps in a flow service, you must open the service in the editor. The flowsteps in the service are listed in the editor. (If you just created the service and it does notyet contain any default logic, the editor is empty).

The INVOKE StepUse the INVOKE step to request a service within a flow. You can use the INVOKE step to: Invoke any type of service, including other flow services and Web service connectors. Invoke any service for which the caller of the current flow has access rights on thelocal webMethods Integration Server. Invoke builtin services and services on other webMethods Integration Servers. Invoke flow services recursively (that is, a flow service that calls itself). If you use aflow service recursively, bear in mind that you must provide a means to end therecursion. Invoke any service, validating its input and/or output.

The BRANCH StepThe BRANCH step allows you to conditionally execute a step based on the value of avariable at run time. For example, you might use a BRANCH step to process a purchaseorder one way if the PaymentType value is CREDIT CARD and another way if it isCORP ACCT.When you build a BRANCH step, you can: Branch on a switch value. Use a variable to determine which child step executes. At runtime, the BRANCH step matches the value of the switch variable to the Label propertyof each of its targets. It executes the child step whose label matches the value of theswitch. Branch on an expression. Use an expression to determine which child step executes. Atrun time, the BRANCH step evaluates the expression in the Label property of eachchild step. It executes the first child step whose expression evaluates to true.

The REPEAT StepThe REPEAT step allows you to conditionally repeat a sequence of child steps based onthe success or failure of those steps. You can use REPEAT to: Re-execute (retry) a set of steps if any step within the set fails. This option is useful toaccommodate transient failures that might occur when accessing an external system(for example, databases, ERP systems, Web servers, or Web services) or device. Re-execute a set of steps until one of the steps within the set fails. This option is useful forrepeating a process as long as a particular set of circumstances exists (for example,data items exist in a data set).

The SEQUENCE StepYou use the SEQUENCE step to build a set of steps that you want to treat as a group.Steps in a group are executed in order, one after another. By default, all steps in a flowservice, except for children of a BRANCH step, are executed as though they weremembers of an implicit SEQUENCE step (that is, they execute in order, one afteranother). However, there are times when it is useful to explicitly group a set of steps. Themost common reasons to do this are: To group a set of steps as a single alternative beneath a BRANCH step. For detailsabout this use of the SEQUENCE step, see To specify the conditions under which the server will exit a sequence of steps withoutexecuting the entire set.

The LOOP StepThe LOOP step repeats a sequence of child steps once for each element in an array thatyou specify. For example, if your pipeline contains an array of purchaseorder line items,you could use a LOOP step to process each line item in the array.To specify the sequence of steps that make up the body of the loop (that is, the set of stepsyou want the LOOP to repeat),

The EXIT StepThe EXIT flow step allows you to exit the entire flow service or a single flow step. Youspecify whether you want to exit from: The nearest ancestor (parent) LOOP or REPEAT flow step to the EXIT flow step. The parent flow step of the EXIT flow step. A specified ancestor flow step to the EXIT flow step. The entire flow service.When you use the EXIT step, you indicate whether exiting should return a successfulcondition or a failure condition. If the exit is considered a failure, an exception is thrown.You can specify the text of the error message that is displayed by typing it directly or byassigning it to a variable in the pipeline.

The MAP StepThe MAP step lets you adjust the contents of the pipeline at any point in a flow service.When you build a MAP step, you can: Prepare the pipeline for use by a subsequent step in the flow service by linking,adding, and dropping variables in the pipeline. Clean up the pipeline after a preceding step by removing fields that the step addedbut are not needed by subsequent steps. Move variables or assign values to variables in the pipeline.