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Subject: RE: [ebxml-cppa] BPSS to WSDL mapping
I generally agree with Dale's comments except as follows:
A WSDL description can be referenced from a CPP through an alternative
process specification reference. A CPA would have to reference two WSDL
descriptions (one for each party) as an alternative to a BPSS instance.
Someone or something would have to determine that the two WSDL descriptions
are compatible. As Dale points out in (3), at this point since there is no
notion in Web Services of service requester descriptions. Has the W3C WSDL
team considered this matter yet?
Regarding (5) below, to be more precise, things in the WSDL binding
overlap CPP, not CPA. A WSDL description describes a service provider's
properties only. It is not an agreement at this point and says nothing
about a service requester.
Regards,
Marty
*************************************************************************************
Martin W. Sachs
IBM T. J. Watson Research Center
P. O. B. 704
Yorktown Hts, NY 10598
914-784-7287; IBM tie line 863-7287
Notes address: Martin W Sachs/Watson/IBM
Internet address: mwsachs @ us.ibm.com
*************************************************************************************
Dale Moberg
<dmoberg@cycloneco To: Cory Casanave <cory-c@enterprise-component.com>, OASIS ebxml-cppa
mmerce.com> <ebxml-cppa@lists.oasis-open.org>, ebtwg-bps@lists.ebtwg.org
cc:
03/11/2002 05:19 Subject: RE: [ebxml-cppa] BPSS to WSDL mapping
PM
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
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