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RE: [Bug 6403] Enumeration: define policy

From: Doug Davis <dug@us.ibm.com>
Date: Tue, 12 May 2009 12:37:05 -0400
To: public-ws-resource-access@w3.org
Message-ID: <OF090D9888.3F9BE4AF-ON852575B4.0058EF6A-852575B4.005B4B7C@us.ibm.com>
Hi Geoff,
  This is actually really close to my proposal - it just changes the NS 
and localName of the QName - however, there are a couple of aspects of 
this solution that prevented me from picking this approach in my original 

First, this will probably require the definition of a 3rd spec for each 
filter dialect.  Let's take the case of XPath.  Let's assume that 
WS-Enumeration were already completed and behind us (and XPath wasn't 
known, as filter, at that time).  If someone wanted to use XPath (which 
has no knowledge of WS-Enum) with WS-Enum, then they would need to define 
(and standardize) this new QName.  This would require a new spec and its 
not clear to me who would take on this responsibility. If it didn't come 
through some org, like w3c, then do we run the risk of each domain 
creating their own QName for the same dialect?  This could hurt interop, 
cause confusion and cause us more work.

Second, I'm wondering if we lose the ability for smart clients to be more 
dynamic because this requires the client to know about all QNames in 
advance.  When parsing the Policy the client would need to know which 
QNames were Filter dialects and which were "something else" (which btw it 
can ignore based on the wsp:Optional attribute). So, if the client wanted 
to present the user with a drop-down box and a list of filter dialects to 
choose from, they could only do it for Filters dialects that were hard 
coded into the system.  Without some way to know that some new QName were 
a Filter dialect, they would be a bit stuck.  In cases where the client 
system itself will need to act on these QNames I think its fair to assume 
that the client must know about each one - however, with Filter dialects 
the client doesn't actually need to act on them.  Its the service that 
does all of the work.  So, in a dynamic environment (like the drop-down 
case I mentioned above) its possible to prompt the user with a list of 
Filter dialect and an entry field (where they can type the expression) and 
the subscriber's client code never actually needs to know anything about 
the Dialect.

This is why ideally I really wanted something like:
        <wsen:FilterDialect uri="...."/>
But of course this would require domain specific policy processing - which 
I don't think anyone wants.  :-)

I think the mechanism in my proposal, while a bit unique, does provide the 
same functionality of your proposal but also covers the concerns I 
mentioned above.
And, it shouldn't cost anything more w.r.t. code since in your proposal 
you're asking the client to know about the QNames in advance, and there's 
no reason why they couldn't know about the QNames using the form I 
proposed.  It just saves the trouble of having to create a new (3rd) spec 
to link WS-Enum with some expression language.

STSM |  Standards Architect  |  IBM Software Group
(919) 254-6905  |  IBM 444-6905  |  dug@us.ibm.com
The more I'm around some people, the more I like my dog.

Geoff Bullen <Geoff.Bullen@microsoft.com> 
05/12/2009 11:51 AM

Doug Davis/Raleigh/IBM@IBMUS
"public-ws-resource-access@w3.org" <public-ws-resource-access@w3.org>, 
RE: [Bug 6403] Enumeration: define policy

We propose the following as clarifying amendments to Doug?s proposal for 
Issue 6403:
The Policy assertion for the XPath filter dialect
<wsen:XPathFilterDialect wsp:Optional? />
The policy assertion represents a requirement to include an XPath filter 
in the WS-Enumeration implementation found at this end point and, 
specifically, that the attribute: 
http://www.w3.org/TR/1999/REC-xpath-19991116 " MUST be specified in 
wsen:Enumerate messages sent to this Web Service.
Per Web Services Policy [WS-Policy], this is compact notation for two 
policy alternatives, one with and one without the assertion. This 
indicates that the behavior indicated by the assertion is optional, 
specifically that a message without an filter dialect is also supported by 
the endpoint.
This is an extensibility mechanism to allow additional attributes to be 
added to the element.
The XPathFilterDialect policy assertion element information item MUST NOT 
include the  wsp:Ignorable attribute in its [attributes] property.
A policy expression containing the XPathFilterDialect policy assertion 
MUST, if present be attached to either a wsdl:binding/wsdl11:binding or 
The normative outline for the Enumeration assertion would be:
<wsen:WSEnumeration [wsp:Optional="true"]? ...>
    <wsen:XPathFilterDialect [wsp:Optional="true"]? />
From: public-ws-resource-access-request@w3.org 
[mailto:public-ws-resource-access-request@w3.org] On Behalf Of Doug Davis
Sent: Monday, April 27, 2009 10:07 AM
To: Geoff Bullen
Cc: public-ws-resource-access@w3.org; 
Subject: RE: [Bug 6403] Enumeration: define policy

Geoff wrote: 
> In general, we are OK with your proposal for Issue 6403.  Here are 
> our general comments on the proposal.  I will be happy to provide 
> more concrete suggestions in a subsequent email as we are heads-down
> processing multiple WS-RA issues at the moment.
> A)   The <x:FilterDialect> is not a concrete policy assertion but a 
> template. This is the first of a kind. How can the WS-RA WG provide 
> an XML Schema definition to specify the syntax of the assertion?
> Why not just define a policy assertion for the XPath filter dialect?

Can you give an example of what you're thinking of?  I think its important 

to do the policy matching w/o needing domain specific code so I'd be 
curious to see what you have in mind. 

> We do not understand what is the justification of the statement:
>    "the namespace of this element is application defined, but the 
> Local Name MUST be "FilterDialect""
> Why is element matching not using namespaces here?

It _does_ use element matching - so I'm not following. 

> >/wsenp:WSEnumeration/wsp:Policy/x:FilterDialect@wsp:Optional
>   This attribute specifies that the assertion is optional per WS-
> Policy. This attribute MUST be present
> B)   The proposal mandates the use of wsp:Optional attribute. But 
> the minimum here would be to allow the use of the attribute and 
> defer the usage of it to service providers.

We can change this, but my thinking was that the use of the Filter 
element and any particular filter dialect (even if just one is 
supported) is optional for the client.  But we can change this 
if people want and assume people are going to be smart enough 
to know that they should really include it - esp. when they support 
more than one dialect. 

> C)   Would it be useful to check if the proposed assertion follows 
> the best practices outlined in the 'Web Services Policy 1.5 - 
> Guidelines for Policy Assertion Authors' doc [1]. 
> At a glance, it appears that the proposal does not follow best 
> practices 6, 8, 9, 15, 20, 29 and 31.

Feel free to do so, but the only one that seems interesting is 
29 and I think I got that covered, but we can use more WSDL-specific 
wording if needed. 
> --Geoff
> [1] http://www.w3.org/TR/2007/NOTE-ws-policy-
> guidelines-20071112/#best-practices-list
> -----Original Message-----
> From: public-ws-resource-access-notifications-request@w3.org 
> [mailto:public-ws-resource-access-notifications-request@w3.org] On 
> Behalf Of bugzilla@wiggum.w3.org
> Sent: Tuesday, April 21, 2009 1:39 PM
> To: public-ws-resource-access-notifications@w3.org
> Subject: [Bug 6403] Enumeration: define policy
> http://www.w3.org/Bugs/Public/show_bug.cgi?id=6403
> --- Comment #4 from Robert Freund <bob@freunds.com>  2009-04-21 20:38:56 
> modified proposal as above with the following:
> insert after :/wsenp:WSEnumeration/wsp:Policy/x:FilterDialect
> An endpoint should include a filterdialect policy assertion for each of 
> filter dialects that it supports.
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Received on Tuesday, 12 May 2009 16:40:34 UTC

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