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Proposal: MEP support in operations

From: Don Mullen <donmullen@tibco.com>
Date: Wed, 20 Nov 2002 13:48:19 -0500
Message-ID: <339902DC0E58D411986A00B0D03D843201B248A6@extmail.rtp.tibco.com>
To: "'www-ws-desc@w3.org'" <www-ws-desc@w3.org>

The following is a proposal for generalizing message exchange pattern
support in WSDL.

Currently an operation's MEP is recognized by examining the order of its
input and ouput children, and is limited to four varieties.  This proposal
recommends instead that the MEP be made explicit by the use of a standard
attribute on 'operation'.  The attribute would be described as follows:

	local name: mep
	namespace name: absent
	type: xs:anyURI

If backward compatibility is desired, then four "standard" URIs might be
created, and associated as the default for operations conforming to their
patterns.  In fact, since output-input and output-only have not been
adequately supported in the past, they might have no default.  The same
might also hold for input-only, which is also relatively underdescribed, in
comparison to input-output (request/response).

This has the advantage of allowing multiple definitions of semantics for
certain patterns, as these prove needed.

In addition, an attribute to 'input' and 'output' would be added in order to
identify the specific role being played in the MEP.  The attribute would be
described as follows:

	local name: messageRole
	namespace name: absent
	type: xs:QName [or xs:anyURI depending on resolution in XMLP re:
property type?]

Example One (Request-Response):

<operation name="GetResponse"
  <input type="GetResponse_Request" messageRole="req-resp:InboundMessage"/>
  <output type="GetResponse_Response"

Example Two (Event-Notification):

<operation name="Event-1"
  <input  type="Subscription_Request" messageRole="event:subscribe"/>
  <output type="Event_Notification" messageRole="event:event"/>
  <input  type="Unsubscribe_Request" messageRole="event:unsubscribe"/>

Note here that the "Event_Notification" could be specified as being 'zero or
more events'.

Don Mullen
TIBCO Software
Received on Wednesday, 20 November 2002 13:51:16 UTC

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