An inline subprocess can be defined as part of a BPEL 2.0 process at the <process> level. The syntax is shown in the following example:

<process name="NCName" targetNamespace="anyURI" 
         xmlns="http://docs.oasis-open.org/wsbpel/2.0/process/executable" ...>
    <!--
     ! All sub-process definitions must appear prior to the WS-BPEL artifacts of
     ! the process definition.
    -->

    <!-- Inline sub-process definition at process scope -->
    <bpelx:inlineSubProcess xmlns:bpelx="http://schemas.oracle.com/bpel/extension"
      name="NCName">*
      ...
      <!-- Partner links and variables serve as sub-process arguments -->
      <partnerLinks>?
        <partnerLink name="NCName" partnerLinkType="QName" myRole="NCName"?
          partnerRole="NCName"?
      bpelx:argumentRequired=["yes"|"no"]? />+
      <partnerLinks>
      ...
      <variables>?
        <variable name="BPELVariableName"  messageType="QName"? type="QName"?
          element="QName"?
                  bpelx:argumentRequired=["yes"|"no"]?>+
          from-spec?
        </variable>
      </variables>
      ...
      <!--
       ! Standard process activity graph here, except that no <receive> or <pick>
       ! activities with createInstance = "yes" are allowed.
      -->
      activity 
    </bpelx:inlineSubprocess>

    <!--
     ! BPEL code stripped for brevity
    -->
</process>

When a BPEL process instance is first created, all subprocess references are resolved. When the process executes a particular call activity, it uses the subprocess resolved at instance creation time. Therefore, two different instances of the same process may use different versions of subprocesses referenced if, for example, the default composite revision for a subprocess changes.

When the BPEL process instance executes the call activity, it is executed within the process's execution space, sharing its state. The call activity transfers control to the subprocess, at which time the subprocess scope is initialized with the argument variables:

• Each parameter is copied (by reference or value, as specified) from the call activity to the subprocess's scope.

• Optional parameters (those with default values) that are not referred to in the call activity's parameter list are initialized with their default values.

• All required parameters must be supplied by the call activity.

• All values supplied by the call activity's parameters must be type-compatible with the corresponding variable (or partner link) defined in the subprocess.

• Each variable (or partner link) in the subprocess can be set only once in a call activity's parameter list.

On completion of the subprocess, control is returned to the parent process. In the normal case, execution continues with the next activity after the call activity. In the case of abnormal subprocess completion, the parent process evolves the process according to the standard life cycle rules of WS-BPEL.

From the monitoring and management view, there is no new process instance for the subprocess created. It is represented by a call activity in the parent process instance. Expanding the activity (navigate) shows subprocess execution details.

To minimize linking errors during runtime, upon deployment of the process and subprocess, references are resolved. Parameter lists are validated as a postdeployment activity. Preprocessing for creating a new process instance validates all subprocess references in the process. If any reference is not resolved, the instance is not created. Instead, an error message is returned, meaning essentially the following:

HTTP Status Code 503, "service not available

Upon a linking error, if the service consumer is waiting, an error message is sent to the consumer that is inline with exit activity handling. Otherwise, the instance is suspended with the reason set as linkage error. If a suitable subprocess is deployed and the reference is resolvable, suspended instances can then be recovered and resume normal execution by automatic recovery.

For information about creating an inline subprocess, see How to Create an Inline Subprocess.