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Re: FW: [Bug 4552] Should the word "collection" be changed to something more specific?

From: David Hull <dmh@tibco.com>
Date: Sun, 20 May 2007 11:55:54 -0400
Message-ID: <46506F8A.70000@tibco.com>
To: "Rogers, Tony" <Tony.Rogers@ca.com>
CC: Asir Vedamuthu <asirveda@microsoft.com>, public-ws-policy@w3.org
For (a somewhat artificial) example:

If I intersect

<All>
  <ExactlyOne>
    <A/>
    <B/>
  </ExactlyOne>
  <ExactlyOne>
    <B/>
    <A/>
  </ExactlyOne>
</All>

with itself, I believe I get a policy that could be represented by the
policy expression

<ExactlyOne>
  <All><A/><B/><B/><A/></All>
  <All><B/><B/><B/><B/></All>
  <All><B/><A/><A/><B/></All>
  <All><B/><A/><B/><A/></All>
  <All><A/><A/><A/><A/></All>
  <All><B/><B/><A/><A/></All>
</ExactlyOne>

Is this correct?

Rogers, Tony wrote:
> Maybe I'm missing something: doesn't an implementation have to
> determine if two assertions are the same when doing a
> policy intersection? I can't see how you can do a policy
> intersection WITHOUT determining if assertions are the same.
>  
> I think I'd have a better understanding if someone explained the
> reasoning behind wanting to put two copies in the intersection result.
> And I doubt I'm the only one.
>  
> Tony Rogers
> tony.rogers@ca.com <blocked::mailto:tony.rogers@ca.com>
>  
>
> ------------------------------------------------------------------------
> *From:* public-ws-policy-request@w3.org
> [mailto:public-ws-policy-request@w3.org] *On Behalf Of *Asir Vedamuthu
> *Sent:* Thursday, 17 May 2007 1:01
> *To:* David Hull
> *Cc:* public-ws-policy@w3.org
> *Subject:* RE: FW: [Bug 4552] Should the word "collection" be changed
> to something more specific?
>
> It is unclear from this mail thread re why the framework should force
> implementations to figure out if two alternatives are same and filter
> them out? Any technical reasons?
>
>  
>
> To be super clear, the quote below is not from me :-)
>
>  
>
> Regards,
>
>  
>
> Asir S Vedamuthu
>
> Microsoft Corporation
>
>  
>
>  
>
> *From:* David Hull [mailto:dmh@tibco.com]
> *Sent:* Tuesday, May 15, 2007 8:48 PM
> *To:* Asir Vedamuthu
> *Cc:* public-ws-policy@w3.org
> *Subject:* Re: FW: [Bug 4552] Should the word "collection" be changed
> to something more specific?
>
>  
>
> Asir Vedamuthu wrote:
>
>     the blanket statement that "collection"
>
>     means "unordered collection with multiple occurrences allowed" is
>
>     inappropriate.
>
>         
>
>  
> Multiple occurrences of the same alternative are okay. The framework treats them as separate alternatives. Can't imagine the technical reasons on why the framework should force implementations to figure out if two alternatives are same and filter them out.
>   
>
> You're defining semantics here, not implementation.  If duplicates
> make no difference, you have set semantics.  If they do, you have bag
> semantics.  If an implementation wants to keep duplicates around,
> that's its business.
>
> By specifying set semantics you are saying that, e.g.,
>
> <ExactlyOne>
>   <All><Foo/></All>
> </ExactlyOne>
>
> means the same as
>
> <ExactlyOne>
>   <All><Foo/></All>
>   <All><Foo/></All>
> </ExactlyOne>
>
> and therefore that no one should write code that depends on one or the
> other form specifically.  Similarly, no one should depend on
> distinctions between <All><Foo/><Bar/></All> and
> <All><Bar/><Foo/></All>.  That doesn't force implementations to
> maintain alternatives in some canonical order, it just defines part of
> the contract for policy authors.
>
> While we're on the topic, it would be good to have a specific use case
> in which <All><Foo/><Foo/></All> is meant to be different from
> <All><Foo/></All>.  If there aren't any, then it would be better to
> replace "collection" with "set" throughout.  For example, the question
> of what does "all of the assertions in both alternatives" mean goes
> away; you just say "union".
>
>  
> If implementers would like to optimize their implementations the framework does not preclude filtering multiple occurrences of the same alternative.
>  
> Regards,
>  
> Asir S Vedamuthu
> Microsoft Corporation
>  
>  
> -----Original Message-----
> From: public-ws-policy-qa-request@w3.org <mailto:public-ws-policy-qa-request@w3.org> [mailto:public-ws-policy-qa-request@w3.org] On Behalf Of bugzilla@wiggum.w3.org <mailto:bugzilla@wiggum.w3.org>
> Sent: Friday, May 11, 2007 8:14 AM
> To: public-ws-policy-qa@w3.org <mailto:public-ws-policy-qa@w3.org>
> Subject: [Bug 4552] Should the word "collection" be changed to something more specific?
>  
>  
> http://www.w3.org/Bugs/Public/show_bug.cgi?id=4552
>  
>  
> dmh@tibco.com <mailto:dmh@tibco.com> changed:
>  
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                  CC|                            |dmh@tibco.com <mailto:dmh@tibco.com>
>  
>  
>  
>  
> ------- Comment #1 from dmh@tibco.com <mailto:dmh@tibco.com>  2007-05-11 15:13 -------
> My understanding from the list discussion is that policies are *sets* of
> alternatives, not bags, in that it does not matter how many times an
> alternative appears, so long as it appears.
>  
> If so, then the blanket statement that "collection" means "unordered collection
> with multiple occurrences allowed" is inappropriate.  If policies are allowed
> to contain the same alternative multiple times, then someone has to say what
> the differences is between, e.g., an alternative occurring once and the same
> alternative occurring twice.
>  
> Conversely, if there is no difference, then say so explicitly.  That is,
> instead of saying "A policy is a collection (unordered, multiples allowed) of
> alternatives where multiplicity doesn't matter", say directly that "A policy is
> a set of alternatives".
>  
>   
>
>  
>
Received on Sunday, 20 May 2007 15:56:17 GMT

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