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Re: ACTION-294 Ashok to open a CR issue with text to define "collection"

From: Fabian Ritzmann <Fabian.Ritzmann@Sun.COM>
Date: Tue, 08 May 2007 22:51:53 +0300
To: Ashok Malhotra <ashok.malhotra@oracle.com>
Cc: "Monica J. Martin" <Monica.Martin@Sun.COM>, "public-ws-policy@w3.org" <public-ws-policy@w3.org>
Message-id: <4640D4D9.8050902@Sun.COM>


To expand on what Monica was replying, if the framework explicitly 
mentions bags, you are restricting the choice of specialized data 
structures. I don't see the benefit in mandating or suggesting a 
specific data structure here. I think it is OK to state that a policy is 
an unordered collection of policy alternatives, but then we should also 
state that it is permissible to collapse equivalent policy alternatives 
and policy assertions into one.


Monica J. Martin wrote:
>> Ashok Malhotra wrote: Fabian:
>> The WS-Policy specification does not talk about implementations.
>> Implementations are free to do what they wish, and will generally use 
>> specialized data structures.  But that not the point.  The spec says 
>> a policy is an unordered collection of policy alternatives which can 
>> include duplicate alternatives.
>> All the best, Ashok
> mm1: I think the point of the question is if it should say that Ashok. 
> Thanks.
>>> -----Original Message-----
>>> From: Fabian.Ritzmann@Sun.COM [mailto:Fabian.Ritzmann@Sun.COM]
>>> Sent: Friday, May 04, 2007 5:49 AM
>>> To: Ashok Malhotra
>>> Cc: public-ws-policy@w3.org
>>> Subject: Re: ACTION-294 Ashok to open a CR issue with text to define
>>> "collection"
>>> To point 3, at least when it comes to WSDL, I don't think duplicate
>>> subjects (i.e. WSDL elements with the same fully qualified name) make
>>> sense. They certainly are not ordered.
>>> Regarding points 1 and 2, wouldn't it be an implementation decision if
>>> duplicates are maintained (bag) or discarded/collapsed (set)? I can't
>>> find any necessity to keep duplicates.
>>> Fabian
>>> Ashok Malhotra wrote:
>>>> My point was that the word 'collection' in Computer Science is used as
>>>> a generic term to cover several types of collections.
>>>> See definition from Wikipedia below. Thus, it would be better to be
>>>> more precise about the exact type of collection we use in WS-Policy:
>>>> In _object-oriented programming_
>>>> <http://en.wikipedia.org/wiki/Object-oriented_programming>, a*
>>>> collection class* is any _class_
>>>> <http://en.wikipedia.org/wiki/Class_%28computer_science%29> that is
>>>> capable of storing other _objects_
>>>> <http://en.wikipedia.org/wiki/Object_%28computer_science%29>.
>>>> Collection classes usually implement some kind of _data structure_
>>>> <http://en.wikipedia.org/wiki/Data_structure>, such as a _list_
>>>> <http://en.wikipedia.org/wiki/List_%28computing%29>, _map_
>>>> <http://en.wikipedia.org/wiki/Associative_array>, _set_
>>>> <http://en.wikipedia.org/wiki/Set_%28computer_science%29>, _array_
>>>> <http://en.wikipedia.org/wiki/Array>, or _tree_
>>>> <http://en.wikipedia.org/wiki/Tree_%28data_structure%29>. A collection
>>>> class is usually able to store an arbitrary number of data items, i.e.
>>>> the size of the collection is adjusted automatically.
>>>> In the framework document we use 'collection' in three contexts:
>>>> 1. "A _policy_ <http://www.w3.org/TR/2007/CR-ws-policy-20070330/> is a
>>>> collection of policy alternatives." Since alternatives can be
>>>> identical and there is no order between them, a policy is a bag of
>>>> alternatives.
>>>> 2. "A _policy alternative_
>>>> <http://www.w3.org/TR/2007/CR-ws-policy-20070330/> is a collection of
>>>> policy assertions." Here, again, the assertions in an alternative can
>>>> be duplicates and are unordered, so bag seems to be the correct term.
>>>> 3. "A _policy scope_
>>>> <http://www.w3.org/TR/2007/CR-ws-policy-20070330/> is a collection of
>>>> policy subjects to which a policy applies." Here I am not sure. Can
>>>> there be duplicate subjects in a policy scope? Aren't policy subjects
>>>> ordered?
>>>> If the policy subjects in a policy scope can be duplicates and are not
>>>> ordered then all uses of 'collection' mean 'bag' and we can add a
>>>> definition such as "In this document the word 'collection' refers to
>>>> what is known in the literature as 'bag'. But I thought we should
>>>> clarify point 3 first.
>>>> All the best, Ashok
Received on Tuesday, 8 May 2007 19:52:11 UTC

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