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RE: Alternatives for resolving subissue 1 in issue i017

From: Yalcinalp, Umit <umit.yalcinalp@sap.com>
Date: Mon, 10 Jan 2005 20:26:39 +0100
Message-ID: <99CA63DD941EDC4EBA897048D9B0061D0F676E09@uspalx20a.pal.sap.corp>
To: "Anish Karmarkar" <Anish.Karmarkar@oracle.com>, <public-ws-addressing@w3.org>

>-----Original Message-----
>From: public-ws-addressing-request@w3.org 
>Sent: Monday, Jan 10, 2005 10:33 AM
>To: public-ws-addressing@w3.org
>Subject: Alternatives for resolving subissue 1 in issue i017
>Here are the alternatives for resolving subissue 1 in issue 
>i017 [1] -- 
>I took an action for doing this during last week's call:
>The subissue is about whether the value of the [action] property is 
>required to be distinct within the scope of WSDL 
>portType/interface when 
>using WSDL to describe the Web service
>Please note that this is an issue only when using WSDL to describe the 
>service and therefore potentially affects only the WSDL 
>binding spec and 
>not the core or the SOAP binding.
>Alternative 1:
>yes, it is required to be distinct within the scope of a WSDL 
>portType/Interface. The spec currently states:
>"An identifier that uniquely (and opaquely) identifies the semantics 
>implied by this message."
>If the values are not distinct within the portType/interface then one 
>has to wonder as to why there are two distinct operations within the 
>portType/interface that have the same semantics? More accurately, the 
>scope should not really be the portType/interface but should also 
>include the directionality of the message, similar to the 
>operation name 
>mapping requirement of WSDL 2.0 [2].

> An added advantage of 
>this is that, 
>the value of the [action] property now can be used to figure out which 
>WSDL-operation is being "invoked" by an incoming message at 
>the service 
>(since operation-names do not manifest themselves on the wire) -- when 
>it is not clear from the contents of the SOAP Body. This has been an 
>interop problem in the past which led to WS-I Basic Profile 1.0/1.1 
>requirement R2710 [3][4].

If I understand you correctly, it seems to me that the combination of
WSDL + WS-Addressing with unique values for the Action property for each
portType/operation/message (direction), the operation name mapping
requirement for WSDL 2.0 will be fullfilled. Right? 

In other words, the default values for Action parameter will also
suffice, but another naming scheme can be employed as long as the
inherent uniqueness rules apply. 

One thing I am wondering is how we can enforce the compliance with this,

A physical address may "host" multiple endpoints, via using the same
address URI value. This allows the same address to be the access point
for to access multiple interface/ports as being the location for
multiple endpoints. By following the requirement stated here and using
the Action value, you can always distinguish the message exchange
uniquely. So, if the domain is a single WSDL, there is no problem. 

A physical address can also host multiple endpoints, not necessarily for
the same WSDL and other exchanges, for obtaining metadata, etc.  If this
were to happen and a scheme other than default values for Action values
were employed, one would have to look at all message exchanges that are
enabled by the physical address, namely across multiple WSDLs, exchanges
for meta-data, private extensions, etc. Therefore, it seems to me that
uniqueness depends on the domain of values you have. 

I am not sure whether we can guarantee uniqueness in this case, just on
a single WSDL. It depends on all the message exchanges that are
supported by a single physical address that supports multiple endpoints,
meta-data, your companies-favorite-out-of-band-without-WSDL thingy.
Therefore, if a physical address can host multiple exchanges and they
are not bounded within a single WSDL, I am not sure whether requiring
uniqueness within a WSDL really buys much, unless there is an inherent
understanding that all Action values for a physical address is
guaranteed to be unique for practical purposes, hence within the
combined domain of Action values, the message exchanges can be
identified uniquely. 

>Alternative 2:
>no, it is not required to be distinct within the scope of a WSDL 
>portType/interface. There might be reasons for allowing non-distinct 
>values <insert-use-case-here>. WSDL interface/operations that 
>do satisfy 
>the distinctness requirement can use the WSDL feature or WSDL 
>extensibility described in [5] (or something similar).

>[I don't think I'm doing justice to alternative 2 as I haven't come 
>across a good usecase for this. If you do have one, please send it to 
>the list]


[3] http://www.ws-i.org/Profiles/BasicProfile-1.1-2004-08-24.html#R2710
[4] http://www.ws-i.org/Profiles/BasicProfile-1.0-2004-04-16.html#R2710
Received on Monday, 10 January 2005 19:28:07 UTC

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