BPEL4WS and IDIOM Decision Suite
The diagram in Figure 1 shows the relationship between these different types of services and the BPEL execution engine. We see these classifications as important when conceptually defining a collaboration of web services.
Figure 1: Relationship between services and the BPEL Engine
The remainder of this document will discuss the role of the IDIOM Decision Suite in providing Decision Services in a BPEL business process execution environment. It is assumed the other services will be built and integrated into a business process using web services development tools (e.g. Glue, Java web services development kit, Eclipse, Visual Studio) and will depend heavily on the technical infrastructure available (i.e. databases, operating systems).
IDIOM as a web service
In summary, there are three alternatives to implement IDIOM as a web service:
- IDIOM standard web service
- Document centric web service
- Type safe message-based web service
The current specification of BPEL4WS is not clear on its support for attachments to the SOAP messages, a feature that is required by the document centric web service approach. WSDL currently provides no mechanism to describe attachments as part of a web service interaction. When invoking a web service directly, the requestor and the service can agree on the presence of a document attachment. While not being described in the WSDL it can be populated and interfaced with directly through SOAP. The insertion of BPEL4WS as an intermediary processor between web services may complicate the support for document attachments. Since WSDL does not describe attachments, and BPEL4WS relies heavily on the WSDL and associated message and container definitions, it is possible that an attachment would not be propagated to collaborating web services. It is assumed that the BPEL4WS container will be responsible for constructing web services interactions (SOAP messages) that are formed by the creation and manipulation of containers and service definitions.
Based on the discussion in the previous paragraph, it has been assumed that for IDIOM to participate in a BPEL4WS managed business process, IDIOM components will need to be implemented as a type safe message based web service.