Re: membershipSubject clarification

Hi Henry,
I have to admit not to follow all of what you wrote. The basic idea is 
that containers have a list of members that are identified by triples of 
the form: membershipSubject membershipPredicate member

By default membershipSubject is the container itself, and 
membershipPredicate is rdf:member but they can be set to something else so 
that a container can be defined "around" a different resource.

More comments below.
--
Arnaud  Le Hors - Software Standards Architect - IBM Software Group

Henry Story <henry.story@bblfish.net> wrote on 05/02/2013 12:40:53 PM:

> From: Henry Story <henry.story@bblfish.net>
> To: Arnaud Le Hors/Cupertino/IBM@IBMUS, 
> Cc: public-ldp-wg@w3.org, Richard Cyganiak <richard@cyganiak.de>
> Date: 05/02/2013 12:41 PM
> Subject: Re: membershipSubject clarification
> 
> 
> On 30 Apr 2013, at 18:11, Arnaud Le Hors <lehors@us.ibm.com> wrote:
> 
> > Hi all, 
> > On Monday we agreed to close Issue-61 which suggested to drop 
> membershipSubject and focus on clarifying the spec instead. 
> > To get us started I'd like to highlight that the editor's draft 
> has an expanded example 3 which may clarify things a bit: 
> > 
> > # The following is an elaborated representation of
> > #   http://example.org/netWorth/nw1
> > @prefix ldp: <http://www.w3.org/ns/ldp#>.
> > @prefix o: <http://example.org/ontology/>.
> > <>
> >   a o:NetWorth;
> >   o:netWorthOf <http://example.org/users/JohnZSmith>;
> >   o:asset 
> >      <assetContainer/a1>,
> >      <assetContainer/a2>;
> >   o:liability 
> >      <liabilityContainer/l1>,
> >      <liabilityContainer/l2>,
> >      <liabilityContainer/l3>.
> > 
> > <assetContainer/>
> >   a ldp:Container;
> >   dcterms:title "The assets of JohnZSmith";
> >   ldp:membershipSubject <.>;
> >   ldp:membershipPredicate o:asset.
> > 
> > <liabilityContainer/>
> >   a ldp:Container;
> >   dcterms:title "The liabilities of JohnZSmith";
> >   ldp:membershipSubject <.>;
> >   ldp:membershipPredicate o:liability. 
> > 
> > This defines two containers (assetContainer and 
> libabilityContainer) corresponding two different membership 
> predicates (respectively o:asset and o:liability) around the same 
> subject resource (netWorth/nw1). 
> 
> 1. does the ldp:membershipSubject have to be a document such as <> ?
> ( which in the example above is a o:NetWorth )
>     a. if yes: how would one add a relation to a thing such as a 
> person <#me> a foaf:Person ?
>     b. if no: why is the relation called membership subject? Does 
> this imply that the o:asset relation is an rdf:subProperty of 
rdf:member.
>       I don't think that if I want to create a document I want to 
> necessarily think of the document I created in say <assetContainer> 
> as being a ldp:member of me.
> 
>   Consider the following example
> 
>    {
>       <#me> a foaf:Person;
>       foaf:depicts <portrait/img1> ;
>       cal:attending <meetings/meet1> .
> 
>        <portrait/> a ldp:Container;
>          dcterms:title "The assets of JohnZSmith";
>          ldp:membershipSubject <#me>;
>          ldp:membershipPredicate foaf:depicts.
> 
>        <meetings/>
>          a ldp:Container;
>          dcterms:title "The liabilities of JohnZSmith";
>          ldp:membershipSubject <.>;
>          ldp:membershipPredicate cal:attending. 
>     } 
> 
>     Is this ok?

I don't think so. The first container is fine, I don't see any problems 
with setting membershipSubject to <#me>. On the other hand <.> would have 
to be the URL of the resource you actually GET, right? So that would be 
something like http://example.org/JohnZSmith and that's not the subject 
you want because there is no <http://example.org/JohnZSmith> cal:attending 
xxx triples.

> 2. Would it not be a good thing if a GET on <portrait/> returned 
thefollowing
> 
>     <> a ldp:Container;
>          dcterms:title "The assets of JohnZSmith";
>          ldp:membershipSubject <#me>;
>          ldp:membershipPredicate foaf:depicts;
>          rdfs:member <img1>, <img2> .
> 
>     and of course if <meetings> mentioned its rds:member ?
> 

The point of membershipSubject and membershipPredicate is to allow 
defining containers that map onto existing resources and allow several 
containers to be defined over the same resource.

> 3. What if I want the object of the relation from the 
> ldp:membershipSubject to the the object to be something described by
> the created 
> resource? Say I want to create a resource that contains a <#me> and 
> the ldp:membershipPredicate should be a foaf:knows relation to the 
object
> ( perhaps a <#him> in the created document? )

What about it? I'm afraid I don't understand this.

> 
> 4. Can I have a number of different membershipSubjects?

Not for a given container.

> 
> Guess
> -----
> 
>   My feeling is that what is wanted is some way to describe how 
> contents of the POSTed
> graph get tied to other resources managed by the server. My feeling 
> is that this is
> a good idea, but orthogonal to the rdf:member of an LDPC. 
> 
> Henry
> 
> > 
> > I would appreciate if Henry and others could ask specific 
> questions about this design so we can try to answer them and see how
> the spec needs to be clarified. 
> > 
> > Thanks.
> > --
> > Arnaud  Le Hors - Software Standards Architect - IBM Software Group
> 
> Social Web Architect
> http://bblfish.net/
>