RE: [ebxml-cppa] BPSS to WSDL mapping

[Dale Moberg <dmoberg@cyclonecommerce.com>]

 Cory, some comments in line. 
 

 Cory>  In a web services seminary this week it became clear that the kinds of capabilities offered by ebXML were directly applicable to enterprise adoption of web services technologies and architectures.  In a panel session it was stated (by an IBM representative) that problems with ebXML were that the adoption was "to fast" and it was "Not linked to WSDL".  Well, we can't go back and slow down the process, but we can fix the latter. 

 

Dale Moberg>The CPPA TC is also investigating how references to WSDL documents (or portions of WSDL documents) might be used by or within future CPPA documents. Please copy our list on your discussions of this issue! One possible way in which WSDL might be referenced within the CPPA was through an alternative ProcessSpecification reference. Other parts of WSDL could be used to populate (and extend) CPPA binding information.

 

 Cory>  Perhaps in this upcoming release we could include a short section that  

 would specify a mapping from BPSS to WSDL.  

  There are three basic issues with this mapping. 

* BPSS specifies two way mappings where as WSDL is one-way

* BPSS allows for nested collaborations

* BPSS has choreography and other semantics. 

 

Dale> I am not certain that I understand the issues  quite the same way:

 

1. WSDL contains both IDL- or API-centric and Document-centric views on

the exchange of information between businesses. 

ebXML has so far done little with the IDL-centric viewpoint. I think something would need to be added to the BusinessDocument (akin to wsdl:Message and the Message's wsdl:part(s) ) to support

setting up this correspondence.) I think you would need to beef up BPSS or at least allow

BusinessDocument extensions to allow wsdl:Message and the Message's wsdl:part(s). These

elements do seem to belong with BPSS constructs, however.

 

2. For the Request-response wsdl:PortType,  the wsdl:input parameters are analogous to a Request, wsdl:output parameters are analogous to a Response, and wsdl:fault is analogous to a Signal. The other three PortTypes may be of interest to BPSS, even though WSDL focuses on 2 PortTypes)

 

3. So a WSDL definition of PortType has its explicit descriptive focus on "one side" of the 'service'. The other side is largely implicit, and is specified only so far as it must be able to supply wsdl:inputs and receive wsdl:outputs (for the wsdl:PortType ofRequestResponse)

 

4. I agree that nesting and choreographies are absent from basic WSDL (as contrasted

with XLang or WSFL ). WSDL appears to view itself as characterizing the atoms of services/flows.

 

5.  WSDL combines some elements that CPPA  has and some that are found within BPSS. I think wsdl:PortType is more a BPSS-like construct. Within the Binding elements (and the 3 Binding extensions for SOAP, HTTP GET/PUT, and MIME), there are some things that overlap CPPA. So to map everything in a WSDL document at the moment, parts would need to go into a BPSS-like document,and parts into a CPPA style document, IMO.

 

 

To create a representation of the WSDL subset of BPSS semantics would  

not be that hard.  It would require the production of WSDL for each "side" of a binary collaboration. 

The nested collaborations could be "flattened" into one WSDL interface or we could use multiple  

separate interfaces.  The choreography and other more advanced BPSS semantics would be lost   

in the WSDL representation but still binding on the services which implement them.

 

This is not a hard task - it could be done in a day or two.  I suggest  

 that for greater acceptance in the industry we consider adding an XSLT 

 transform to produce the required WSDL and make this part of the next revision - very soon.   

 This would help bind ebXML into the web services core technologies.   

 While we (DAT) don't have to bandwidth to do this in the sort time required,  

 we would be happy to assist someone in such a task.

 

Regards,

 

Cory B. Casanave, President

Data Access Technologies

www.enterprise-component.com

(305) 234 7077