idea of rinsing SOAP off the body of BPEL, your agreement with Yaron
also amounts to rejecting Yaron’s proposals for dealing with optional
headers. I assume that is intentionally left unsaid ..
November 19, 2003 9:09 AM
Subject: Re: [wsbpel] Issue - 77
- Under specified operation definitions
I have to
agree with you; the only sane course of action here is to demand that
any message constructs that BPEL can use must be described in WSDL,
otherwise BPEL is blind to them. This doesn't prohibit lower-levels of
a "stack" from mucking around with the message further, injecting or
processing headers as needs be. We sure don't want to be in business
of building exceptions to this rule into the BPEL vocabulary!
I'm a little leary about having processes
directly mess around with secondary protocols (i.e. headers). A
process could easily become overwhelmed with chewing on and processing
headers, signatures, assertions, and the actual business process being
implemented could become unreadable. Do we want, at a business level,
to be messing around with such low-level protocols? My sense is that
BPEL ought to work at a higher level of abstraction, if it is to be
used to express business processes rather than a lot of technical
Getting back on topic:
some confusion arises with the confusion of SOAP with WSDL. I know
that SOAP and WSDL could have been better designed to keep this
clearer, but the fact is some (many, perhaps?) associate web services
only with SOAP, and look at BPEL as, in part, a way to play directly
with SOAP messages. This is a misleading way to look at it, just
as it is misleading to regard SOAP as just HTTP. Let's just rinse all
that SOAP off our thinking, and stick with nice, clean WSDL.
Yaron Goland wrote:
Issue - How do to deal with message content that is not specified in the
WSDL abstract operation definition?
For example, if a BPEL process receives a SOAP message with a SOAP
security header that wasn't specified in the WSDL abstract operation
definition then how does the BPEL process reach into the header and pull out
the name of the sender so that the BPEL process can send a message such as
"I just got a signed message from Joe"?
The inverse example is also possible. The BPEL engine may have been
given a standard WSDL definition that does not specify the use of a callback
header in the WSDL abstract operation definition. If the BPEL process needs
to insert such a header, how does it do it?
The original issue that started this thread
provides another example of the problem that uses some fairly naughty but
not apparently illegal WSDL behavior.
There would seem to be two fairly straight forward solutions to the issue -
Introspection or re-write the WSDL.
Introspection would require us to introduce a new BPEL activity that could
somehow plum a message so that it is possible to 'see' parts of the concrete
message that are not present in the abstract operation definition. Similarly
we would need to be able to edit the concrete message before it goes out in
order to include content that wasn't defined in the WSDL abstract operation
definition. The complexity of introspection makes for what appears to me to
be a solution that is much worse than the problem.
The other solution is to require that people re-write their WSDLs. If you
want to receive message content that isn't in the abstract operation
definition you were given then you need to edit the WSDL you feed your BPEL
engine to include that content in its abstract operation definition. The
same logic applies to sending messages with content that wasn't specified in
the original WSDL abstract operation definition.
Re-writing WSDLs may not be pretty but introducing introspection seems
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