Re: Issue 6712 Discussion and Proposal

This does not address the usecase that I'm worried about [1] nor the 
issue.  Even HTTP itself has a "message format" flag - its called 
"Content-Type".  In cases where there are multiple ways to interpret the 
data (which is something that Transfer itself promotes) it only seems 
logical for Transfer to provide the mechanism by which users of the spec 
can do that.  We don't need to specify much since the QName of the child 
can tell you most everything you need to know - however, the one case of 
the resource being an xs:any is still left ambiguous.

[1] 
http://lists.w3.org/Archives/Public/public-ws-resource-access/2009Apr/0142.html

thanks
-Doug
______________________________________________________
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Geoff Bullen <Geoff.Bullen@microsoft.com> 
Sent by: public-ws-resource-access-request@w3.org
05/05/2009 01:05 PM

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"public-ws-resource-access@w3.org" <public-ws-resource-access@w3.org>
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Subject
Issue 6712 Discussion and Proposal






After further consideration of Issue 6712 (
http://www.w3.org/Bugs/Public/show_bug.cgi?id=6712), which concerns the 
Create message in Transfer, we don?t really think it matters if the spec 
is inferring that a given service or resource can support more than one 
format of Create Message or not.  First, a few assumptions:
a)     Each Service is ultimately responsible for deciding what type and 
format of information is sent in a Create message.
b)     Each Service will define its own set of ?creation rules? (if any) 
which will be used to create its resources.  That is, the WG will not 
define some common creation rules language that will be used by all 
resources.  A Service may even support more than one format of creation 
rules if it wants to.
 
Since the service is responsible for providing the definition of each 
Create message format it supports, it is also responsible for demining how 
it will tell the difference between those multiple formats when they occur 
in a Create message.   One way that the service might easily do this is as 
follows:
 
Defining the literal Resource to create:
[Header]
               <wsam:Action>?/ws-tra/Create</wsam:Action>
[Body]
<Create>
               <xxx:MyResource>
                              Resource Definition here
               </xxx:MyResource>
</Create>
 
Defining a set of rules to create a Resource:
[Header]
               <wsam:Action>?/ws-tra/Create</wsam:Action>
 [Body]
<Create>
               <xxx:MyRules>
                              Rules here
               </xxx:MyRules>
</Create>
 
In the end, there is no real difference between these two examples. It is 
not clear then what the value is in providing a means within the protocol 
for determining the message format (e.g. a resource or rule flag).  Since 
the resource (service) is responsible for the definition of both 
?MyResource? and ?MyRules? there is literally nothing extra in the 
Transfer protocol that is needed to help the resource understand the type 
of ?instructions? it has been sent in a Create message.  To add some flag 
to the Transfer protocol seems purely redundant and unnecessary.
 
Based on the feedback from the WG, it does seem like some clarifying text 
is required, we propose:
 
[Body]/wst:Create
 
This REQUIRED element MAY contain zero or more child elements. If this 
element does not contain a child element then the resource will be created 
using default values. The first child element, if present, is 
service-specific (or the interpretation of the first child element is 
defined by the resource to which the create message is addressed) and MUST 
be the literal resource representation, a representation of the 
constructor for the resource, or other instructions for creating the 
resource. Additional extension elements MAY be included only after the 
mandated first child element.
 
--Geoff