This page provides information on WSO2 BPS's compliance to the final WS-BPEL 2.0 specification released by OASIS.
Variable Initialization
Variable initialization using in-line spec is fully supported. (WS-BPEL 2.0 Section 8.1: http://docs.oasis-open.org/wsbpel/2.0/OS/wsbpel-v2.0-OS.html#_Toc164738495)
External Variables
In addition to regular variables that are managed by the engine according to the BPEL specification, Ode adds support for variables whose content is stored externally, yet transparently accessible from the engine.
Activities
Divergences from the WS-BPEL 2.0 specification (http://docs.oasis-open.org/wsbpel/2.0/OS/wsbpel-v2.0-OS.html) for each standard BPEL activity is described below along with the activities that are compliant.
<throw>
The <throw> activity is fully compliant with the specification.
<exit>
The <exit> activity is fully compliant with the specification.
<wait>
The <wait> activity is fully compliant with the specification.
<empty>
The <empty> activity is fully compliant with the specification.
<sequence>
The <sequence> activity is fully compliant with the specification.
<if>
The <if> activity is fully compliant with the specification.
<while>
The <while> activity is fully compliant with the specification.
<repeatUntil>
The <repeatUntil> activity is fully compliant with the specification.
<flow>
The <flow> activity is fully compliant with the specification.
<receive>
There are several major issues with support for the <receive> activity. Since WSO2 BPS does not yet support the <fromPart> syntax, the variable attribute must be used. Furthermore, only message variables can be referenced with the variable attribute, whereas the specification permits referencing of an element-typed variable, if the WSDL for the request message contains a single element-typed section.
Multiple start activities as described in section 10.4, and 15.4 (http://docs.oasis-open.org/wsbpel/2.0/OS/wsbpel-v2.0-OS.html#_Toc164738541) of the specification are not officially supported. This precludes the use of initiate="join". WSO2 BPS does not provide the ordering guarantees described in section 10.4 of the specification. Also, it does not enforce the ordering requirements described in the same section. Therefore, the BPEL code below is illegal according to the BPEL specification, but allowed by WSO2 BPS.
<flow>
<receive ... createInstance="yes" />
<assign ... />
</flow>
The specification defines two standard faults ? bpel:conflictingRequest and bpel:conflictingReceive ? to deal with two similar error conditions relating to multiple outstanding requests on a single partner-link/operation/messageExchange tuple. WSO2 BPS does not distinguish between these two conditions and 'conflictingReceive' is thrown whenever either of the conditions occurs. That is to say, in certain cases a conflictingReceive indicates a conflictingRequest, and conflictingRequest is never thrown.
Finally, the validate attribute, if present, is ignored. WSO2 BPS currently provides no variable validation.
<pick>
The <pick> activity has the same issues as the <receive> activity.
<reply>
The conformance issues with the <reply> activity mirror those of the <receive> activity as described above. The <toPart> syntax is not supported, and variable attributes must reference message-typed variables.
<invoke>
Again, as in the <receive> and <reply> activities, the <toPart> and <fromPart> syntax are not supported. Similarly, the inputVariable and outputVariable attributes must reference message-typed variables. Here too, the validate attribute is ignored.
<compensateScope>
The <compensateScope> activity is fully compliant with the specification.
<rethrow>
The <rethrow> activity is fully compliant with the specification.
<validate>
The <validate> activity is not implemented by WSO2 BPS. Processes containing such activities will cause a compilation failure.
<extensionActivity>
Activity extension is fully supported in WSO2 BPS.
<forEach>
The <forEach> activity is fully compliant with the specification. WSO2 BPS supports both sequential and parallel for-each semantics.
<scope>
Isolated scopes are implemented in ODE trunk and available with WSO2 BPS 1.1.0 as a result.
<compensate>
The <compensate> activity is not compliant with the specification. In WSO2 BPS, this activity has the same effect and syntax as <compensateScope>. In addition, the scope attribute may be used in place of the target attribute with the same effect; and WSO2 BPS expects one of these attributes must be specified.
<assign>
Given below are the known divergences from the specification relating to the <assign> activity.
- The WS-BPEL 2.0 specification requires the <assign> activity to be atomic. Currently in WSO2 BPS, each <copy> is atomic.
- The specification provides for validating variables at the end of an assignment using the validate attribute. WSO2 BPS does not support this, meaning that the bpel:invalidVariables fault is never thrown by an <assign> activity in WSo2 BPS.
- Inline assignment as part of the variable declaration isn't currently supported.
Ode currently uses the expressionLanguage attribute to determine the language used in assignments instead of using the queryLanguage attribute. WSO2 BPS provides certain (non-standard) extensions to the <assign> activity that do not conform to the specification's requirements for assignment extensions. Some of them are discussed through the following synopsis.