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RE: Issue i017 - Purpose of the Action property -- my action item

From: Tim Ewald <tim@mindreef.com>
Date: Tue, 21 Dec 2004 09:13:13 -0500
To: "'Anish Karmarkar'" <Anish.Karmarkar@oracle.com>, <public-ws-addressing@w3.org>
Message-ID: <E1CgklI-0006gw-Mm@frink.w3.org>

> 1) The [action] property is supposed to uniquely identify the 
> semantics implied by the message. Since the value of this 
> property is fixed by the WSDL description (either through the 
> defaulting mechanism or through the use of wsa:Action 
> attribute), this value is really per message type within an 
> MEP/operation/transmission primitive. Note that there are 
> semantics associated with the MEP/operation grouping within 
> an interface/portType as well as semantics associated with 
> the individual input/output/fault message defined in WSDL. 
> Why is it necessary to provide a mechanism, specifically the 
> wsa:Action attribute, which overrides the default (where the 
> default algorithm does produce a unique value)? What is the 
> usecase for this? At the very least identical
> (wsa:Action) attribute values should be disallowed, otherwise 
> the [action] property will not uniquely identify the 
> semantics implied by the message (type).

By overriding the default action URI, a service can use well-known
messages/actions that can be consumed by clients in a portType-independent
way. For instance, consider WS-MetadataExchange, which has a well-known
message/action to get metadata from a service. I want my service to expose
that behavior to a clients without the consumer having to know what my
portType is (it won't know until it gets my service's metadata). If only
default actions are allowed, this model for generic behaviors will not be
supported UNLESS a service described in WSDL 1.1 implements multiple ports
(one for WS-MEX and one for its own interface) or in WSDL 2.0 derives from
multiple interfaces.

Received on Tuesday, 21 December 2004 20:43:28 UTC

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