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Re: What does "being a member" mean?

From: Henry Story <henry.story@bblfish.net>
Date: Mon, 11 Nov 2013 19:45:54 +0100
Cc: Alexandre Bertails <bertails@w3.org>, Linked Data Platform WG <public-ldp-wg@w3.org>
Message-Id: <30365D03-BA61-4D48-881E-712DF2469FB9@bblfish.net>
To: Steve Battle <steve.battle@sysemia.co.uk>

On 11 Nov 2013, at 19:22, Henry Story <henry.story@bblfish.net> wrote:

> 
> On 11 Nov 2013, at 18:36, Steve Battle <steve.battle@sysemia.co.uk> wrote:
> 
>> I thought that "being an LDPR" meant "being a member of an LDPC".
>> 
>> Questions about Barbers and people who don't shave themselves
>> notwithstanding, there's at least one LDPC, and hence an LDPR by
>> implication, that is not a member of a LDPC.
> 
> This shows that the notion of an LDPR is logically prior to that 
> of membership, and that LDPCs are causally prior to their members .
> 
> Anyway there are some definitions in the spec:
> 
> [[
> Linked Data Platform Container (LDPC)
> An LDPR representing a collection of membership triples which is uniquely identified by a URI that responds to client requests for creation, modification, and enumeration of its members.
> 
> Membership triples
> A set of triples in an LDPC's state that lists its members. A container's membership triples all have one of the following patterns:
> membership-constant-URI	membership-predicate	member-URI
> member-URI	membership-predicate	membership-constant-URI
> The difference between the two is simply which position member-URI occupies, which is usually driven by the choice of membership-predicate. Most predicates have a natural forward direction inherent in their name, and existing vocabularies contain useful examples that read naturally in each direction. rdfs:member and dcterms:isPartOf are representative examples.
> Each container exposes properties that allow clients to determine which pattern it uses, what the actual membership-predicate and membership-constant-URI values are, and (for containers that allow the creation of new members) what value is used for the member-URI based on the client's input to the creation process.
> ]]
> 
> The spec then tells us how to "create, modify and enumerate" members. But the spec does this by 
> describing actions on LDPRs using GET, POST and DELETE. GET enumerates the members, DELETE deletes
> a member, POST creates one.
> 
> What is missing in the spec is the definition of the ldp:member relation that relates the LDPC to
> the LDPRs on which the above actions can be exercised to change the membership triples. We can define
> it and thereby make things much clearer. Let me propose the following ldp:member definition
> 
> ldp:member a rdf:Property;
>   ldp:domain ldp:Container;
>   ldp:range ldp:Resource; 
>   ldp:comment """
>     An ldp:member of a ldp:Container is a LDOR which is created when a POST succeeds 
>     on it (creates via the membership triples) or which when DELETED removes the membership 
>     triples."""
> 
> ldp:created refs:subPropertyOf ldp:member;
>   ldp:comment "relates an ldp:Container to a LDPR which is created when a POST succeeds" .
> 
> The ldp:member relation is useful to make it clear what the LDPRs on which to act
> to change the membership triples.
> 
> If we can agree on this then we can have clearer conversations perhaps.

I put up the definition, with some obvious fixes, in the wiki here:

  http://www.w3.org/2012/ldp/wiki/Member

So that we can re-use it in later discussions.

> 
> Henry
> 
>> 
>> Steve.
>> 
>> -----Original Message-----
>> From: Alexandre Bertails [mailto:bertails@w3.org]
>> Sent: 11 November 2013 16:49
>> To: Linked Data Platform WG
>> Subject: What does "being a member" mean?
>> 
>> Guys,
>> 
>> I think we have a problem with semantics :-)
>> 
>> Can somebody tell me what "being a member" means?
>> 
>> I thought that "being an LDPR" meant "being a member of an LDPC".
>> 
>> How is that different from "being managed by an LDPC"? And from
>> "ldp:created"?
>> 
>> Are the LDP interactions driven by "being a member" or by "being an
>> LDPC/LDPR"?
>> 
>> Is the notion of membership achieved through membershipXXX? If not, what's
>> the name for the feature captured by the membershipXXX relations?
>> 
>> If a POST succeed, does it mean that the new resource is created, or
>> managed, or a member of the LDPC? What about a binary resource then, as
>> it's currently not considered as an LDPC?
>> 
>> Sorry if those are obvious questions, but when I hear the conversations we
>> have in the meetings, it looks pretty confused :-/
>> 
>> Alexandre.
>> 
> 
> Social Web Architect
> http://bblfish.net/

Social Web Architect
http://bblfish.net/
Received on Monday, 11 November 2013 18:46:31 UTC

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