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Subject: Moving on Addressing
would like to propose is that we consider aligning CAF's addressing
requirements with WSDL as closely as possible in order to achieve four
objectives: eventual migration to standardized addressing, a useful way
about web services, addressing information independent from the message
and a static declaration of relationships between port types in WSDL. I
we what we need to define is something simple enough to satisfy the
requirements of CAF and nothing more. I don’t believe that we can make
WS-Addressing in this context as it’s currently a proprietary
detached from any standards efforts.
formal technical details of whatever we do can be hashed out in a
group. For now, I’d like to put some ideas on the table and make there
consensus that we need something more than what is in the current
specifications. First, I'd like to make it clear why each of these
we want broad interoperability with as much infrastructure as possible.
objective is perhaps the most difficult since there currently is no
mechanism for SOAP message addressing, so I assume that it is a goal
than a requirement. However, there is movement in this area in the WSDL
group and I propose that we use WSDL as the basis of our addressing
so far as possible. If all goes well, we can work to achieve broad
interoperability as well as ease of consumption of addressing
endpoint infrastructure and intermediaries. In the worst case, we will
own addressing solution in the end, but one that makes sense.
to have a way to talk about services, since services consume the
are sending around. The current submitted CAF documents use a URL to
a service (a bit of a simplification, but basically accurate). This is
useable as multiple services may share the same URL. There is also an
extensibility element that I presume is meant to act like an Object Key
CORBA, but that is meaningless to web services and should be avoided.
be better to use something that is based on WSDL. For our purposes, the
important outcome of current WSDL deliberations is this: the
may be used as the basis for providing service references. A service
provides complete definition of the service itself and is a perfectly
mechanism for establishing dynamic relationships between services; we
could also provide "strongly typed" references in message payloads.
needs to formally resolve whether it will be dependent on WSDL 2.0 or
I believe that we can make this work for referencing with WSDL 1.1 if
require that the service implement only a single PortType.
Information In SOAP Body
look at the schema for WS-CAF, the addressing information is passed
the SOAP body. This is bad for a number of reasons. It creates brittle
solutions (eg, demarshalling errors in the SOAP body can not be
More importantly, it's simply a bug to include system level
SOAP bodies. We should move the addressing information to SOAP headers.
are no standardized headers, so we will need to invent some in the
If standardization occurs, we can move pick up those addressing header
definitions. We could make do with the following headers:
A reference to a
MessageId. This may be used for correlation.
A brief example is included in the end of this email.
Relationships Between Services
consumer of the specifications as they stand is left to interpret the
relationship between operations defined in different abstract WSDL
It would be desirable for both human users and for tools to define
relationships between those operations as a full-fledged message
pattern that are machine interpretable, or at the very least
the messages that the operations send asynchronously. Of course the
specification text could (and should) spell out the relationships, but
less useful since the web services runtime platform is barred from
any of the addressing functions. There is no way to do this at all in
I’m going to punt on this one and suggest we wait for a few months to
there are any developments to help us here since this is nonessential
Example SOAP Header (not quite correct for simplicity):
that this allows us to talk unambiguously about services and messages.
Presumably, other headers would include a reply destination and a fault
destination, though the two may be redundant. And of course the
directives are not a part of the SOAP body.
Again, I would like us to have a subgroup that deals with these issues in detail, so please regard this as a launching point for those discussions only.