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:



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------- 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".