WSO2 BPS - WS-BPEL Compliance

WS-BPEL 2.0 Specification Compliance

This page provides information on WSO2 BPS's compliance to the final WS-BPEL 2.0 specification released by OASIS.

Variables

Initialization

Variable initialization using in-line from-spec is fully supported. (WS-BPEL 2.0 Section 8.1)

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. See External Variables for more information.

Activities

Divergences from the WS-BPEL 2.0 specification for each standard BPEL activity is described under this section.

<receive>

There are several major issues with support for the <receive> activity.

WSO2 BPS does not yet support the <fromPart> syntax. Therefore, 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 part.

Multiple start activities as described in section 10.4, and 15.4 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. Hence, the BPEL code

            <flow>
            <receive ... createInstance="yes" />
            <assign ... />
            </flow>
        

is illegal according to the BPEL specification, but allowed by WSO2 BPS.

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.

<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.

<assign>

The WS-BPEL 2.0 specification requires the <assign> activity to be atomic. Currently in WSO2 BPS, each <copy> is atomic.

The specification also provides for validating variables at the end of an assignment using the validate attribute. WSO2 BPS does not support this. This means that the bpel:invalidVariables fault is never thrown by an <assign> activity.

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.

There are no other known divergences from the specification relating to the <assign> activity that would prevent the execution of valid BPEL assignments. WSO2 BPS provides certain (non-standard) extensions to the <assign> activity that do not conform to the specification's requirements for assignment extensions. Consult the reference page for the <assign> activity for further details regarding non-standard extensions.

<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.

<forEach>

The <forEach> activity is fully compliant with the specification. WSO2 BPS supports both sequential and parallel for-each semantics.

<pick>

The <pick> activity has the same issues as the <receive> activity.

<flow>

The <flow> activity is fully compliant with the specification.

<scope>

Isolated scopes are implemented in ODE trunk and hence will be available with WSO2 BPS 1.1.0

<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.

<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. Processescontaining such activities will cause a compilation failure.

<extensionActivity>

Activity extension is fully supported in WSO2 BPS.