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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: Tue, 15 May 2007 23:48:05 -0400
Message-ID: <464A7EF5.2070202@tibco.com>
To: Asir Vedamuthu <asirveda@microsoft.com>
CC: "public-ws-policy@w3.org" <public-ws-policy@w3.org>
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] On Behalf Of bugzilla@wiggum.w3.org
> Sent: Friday, May 11, 2007 8:14 AM
> To: 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 changed:
>
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                  CC|                            |dmh@tibco.com
>
>
>
>
> ------- Comment #1 from 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 Wednesday, 16 May 2007 03:48:21 GMT

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