Am I missing something here?
Suppose for a moment that you ignore that "anonymous" reply channel in
HTTP, and every message uses WS-Addressing for a response (although
potentially it uses the "anonymous" channel).
How is this problem of callbacks over WS binding different from the
four (five? six?) week effort on JMS that we (but mostly Simon H.) went
through trying to figure out how to handle the JMSReplyTo header,
depending on MEP, and callbacks? With JMS there is a clear upside to
using the JMSReplyTo header, in that it is already a "Destination",
thus overcoming some potential limitations.
If this is the same problem, does it deserve a solution that follows
the same pattern? Or, is it a characteristically different problem (as
I think it is), in that there isn't any "blessed" "reply" header that
is any more special than any other.
-Eric.
Michael Rowley wrote:
I’d like to
get this topic started. I’ve
narrowed the subject line from the original Issue 22 title, since I’d
like this
particular thread to be on how callbacks could be handled in the WS-*
world. We
can handle conversations and other bindings on other threads.
First, I’ll
assume that we will try to use
WS-Addressing,
if possible.
My first
thought is that it would be
preferable to be able to leverage the ws-ReplyTo field, since I believe
that it
should be possible to distinguish replies from callbacks, and I also
believe
that callbacks should go to the same place that replies would go to. I
have a
vague recollection that Anish preferred the use of <wsa:from>
rather than
<wsa:replyTo> for passing callback ID information.
Unfortunately, I can’t
find an email to that effect, so I’ll ask that he confirm or deny that.
I've been
thinking that the client that is
going to receive callbacks might want the reference parameters that
would be
available if the service provider follows the rules from the
"Formulating
a Reply Message" section of the WS-addressing spec.
One way that
a callback could be
distinguished from a reply is that the callback could have a
<relatesTo>
header that uses a relationship type of "oasis.org/isCallbackFor" and
a reference to the messageID that the callback is in response to. I
haven’t
seen other uses of the <relatesTo> header, but it seems like this
is exactly
the sort of thing it is meant for.
Michael
From: Eric
Johnson
[mailto:]
Sent: Monday, February
04, 2008
2:45 PM
To: Mike Edwards
Cc: OASIS Bindings
Subject: Re:
[sca-bindings]
ISSUE-22: The Bindings specifications should provide exemplary
Implementations
for a) Callbacks and b) Conversations
Logged
as http://www.osoa.org/jira/browse/BINDINGS-22
-Eric.
Mike Edwards wrote:
Raiser:
Mike Edwards
Target:
Web Services Binding
specification, JMS Binding Specification, JCA Binding Specification
Description:
At
present, it is not clear which, if any, of the Bindings specifications
enable
the implementation of two important
features
of SCA described in the Assembly specification - namely Callback
interfaces and
Conversational
interfaces.
Each
of the Bindings specifications should explicitly declare if it is
possible to
support each of these features.
For
each of the Bindings specifications that claim to support either or
both of
these features, the specification
should
provide a full description of at least one exemplary implementation of
the
feature using the Binding
technology
described in the specification. Multiple alternative implementations
are
permitted and may be
added
to the specification.
For
example, it may be possible to implement Callbacks using WS-Addressing
capabilities with Web services.
If
so, and example, showing the use of appropriate features of
WS-Addressing and
other relevant WS-*
capabilities
should be added to the specification. If an alternative exists using
(say) WS-Context, then an
example
based on that technology can also be provided.
Proposal:
None
at present.
Yours, Mike.
Strategist - Emerging Technologies, SCA & SDO.
Co Chair OASIS SCA Assembly TC.
IBM Hursley
Park, Mail Point 146, Winchester, SO21 2JN, Great
Britain.
Phone & FAX: +44-1962-818014 Mobile: +44-7802-467431
Email:
Unless
stated
otherwise above:
IBM United Kingdom Limited - Registered in England
and Wales
with number 741598.
Registered office: PO Box
41, North Harbour, Portsmouth, Hampshire PO6 3AU
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