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Re: What does "being a member" mean?

From: Ashok Malhotra <ashok.malhotra@oracle.com>
Date: Fri, 22 Nov 2013 17:27:32 -0500
Message-ID: <528FDA54.5050003@oracle.com>
To: public-ldp-wg@w3.org
Henry:
A couple of points:
1.  There is a view that collections are merely views over the triples hosted by the server.
That is, a selection of triples by subject and predicate.  Your proposal links the collection
and its members directly which is contrary to this view.
2.  ldp:created would only apply to members created by doing a POST to a collection.
What about members created by other means?  What about non-RDF members?
All the best, Ashok

On 11/22/2013 2:34 PM, Henry Story wrote:
> On 22 Nov 2013, at 16:40, Eric Prud'hommeaux <eric@w3.org> wrote:
>
>> * Arnaud Le Hors <lehors@us.ibm.com> [2013-11-21 11:21-0800]
>>> Hi all,
>>> In an effort to clarify what we currently have in the spec I put a page
>>> together on our wiki that I invite you all to read:
>>>
>>> http://www.w3.org/2012/ldp/wiki/Membership
> Impact of making ldp:created mandatory in all cases
> ===================================================
>
> http://www.w3.org/2012/ldp/wiki/Membership#Impact_of_making_ldp:created_mandatory_in_all_cases
>
> 1. Query Simplicity
> -------------------
>
> It says that the query becomes:
>
> [[
> PREFIX ldp: <http://www.w3.org/ns/ldp#>
>
> SELECT ?ldpc ?resource
> WHERE {
>        ?ldpc a ldp:Container;
>          ldp:created ?resource.
> }
> ]]
>
> In fact the query can be simplified to
>
> [[
> PREFIX ldp: <http://www.w3.org/ns/ldp#>
>
> SELECT ?ldpc ?resource
> WHERE {
>        ?ldpc ldp:created ?resource.
> }
> ]]
>
> since the domain of ldp:Created is an ldp:Container .
>
> ( When querying an LDPC the query can be made even more specific by asking
>
> [[
> PREFIX ldp: <http://www.w3.org/ns/ldp#>
>
> SELECT ?resource
> WHERE {
>        <> ldp:created ?resource.
> }
> ]]
> )
>
> 2. duplication
> --------------
>
> The text says "This simplifies queries at the cost of extra membership arcs. "
> I disagree. If anything ldp:created should be a sub relation of rdfs:member.
> ie:
>
>    ldp:created rdfs:subPropertyOf rdfs:member .
>
> Therefore all the duplicates can be ignored. Ie one only needs the container
> to be:
>
> [[
> @base <http://example.org/container1/>
> @prefix dcterms: <http://purl.org/dc/terms/>.
> @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
> @prefix ldp: <http://www.w3.org/ns/ldp#>.
>
> <>
>     a ldp:Container;
>     ldp:containerResource <> ;
>     ldp:containsRelation rdfs:member;
>     ldp:insertedContentRelation ldp:MemberSubject;
>     dcterms:title "A very simple container";
>     ldp:created <member1>, <member2>, <member3>.
> ]]
>
> 3. in perspective of ldp-ISSUE-85 (causation) & ISSUE-89 (ldp:xyz)
> ------------------------------------------------------------------
>
> To go one step further, I would argue that if one thinks of
> ldp:containerResource, ldp:containsRelation and ldp:insertedContentRelation
> as forming a rule on what should happen when one POSTs, and not a way to infer
> from membership triples to ldp:created resources ( or more generally to ldp:xyz
> resources as defined by ISSUE-89 ) then one can simplify the above to the
> following
>
>   
> [[
> <> a ldp:Container;
>      ldp:created <member1>, <member2>, <member3>.
> ]]
>
> or considering ISSUE-89
>
> [[
> <> a ldp:Container;
>      ldp:xyz <member1>, <member2>, <member3>.
> ]]
>
> which of course would be easier to read as
>
> [[
> [[
> <> a ldp:Container;
>      ldp:manages <member1>, <member2>, <member3>.
> ]]
>
> That is the point of ISSUE-85
>
>
>
>> Executive summary:
>>   example data for all patterns of membership triples.
>>   SPARQL queries which reach all members regardless of pattern.
>>   comparison with ldp:manages proposal.
>>
>>
>>> I'm hoping this will help the discussion moving forward as it is relevant
>>> to all the issues that we have on our agenda for Monday:
>>>
>>>     ISSUE-84 ldp:member
>>>     ISSUE-85 membershipXXX rules
>>>     ISSUE-86 "membership triples" misnamed
>>>     ISSUE-89 Managed resources
>>>
>>> Regards.
>>> --
>>> Arnaud  Le Hors - Software Standards Architect - IBM Software Group
>> -- 
>> -ericP
>>
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>> mobile: +33.6.80.80.35.59
>>
>> (eric@w3.org)
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>>
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Received on Friday, 22 November 2013 22:28:03 UTC

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