[oslc-core] Rethinking link labels without reified statements

[Steve K Speicher]

Based on review on the mailing list and at last Core WG call, I consider 
this to be closed with no changes.  Just summarizing with the following 
observation:

1. We are not using anything that is really being scoped out of the new 
work by W3C RDF WG, for example we only use rdf:* class/predicates and 
blank nodes. 
2. There really isn't an acceptable alternative.  Alternatives require us 
to reach a similar conclusion to what is defined using reification.

I will continue to track RDF WG activity with reification with this usage 
in mind.

Thanks,
Steve Speicher | IBM Rational Software | (919) 254-0645

> From: Steve K Speicher/Raleigh/IBM at IBMUS
> To: oslc-core at open-services.net, 
> Date: 06/12/2012 03:11 PM
> Subject: [oslc-core] Rethinking link labels without reified statements
> Sent by: oslc-core-bounces at open-services.net
> 
> In looking at what is on the roadmap for the W3C RDF Working Group in 
> considering deprecating reified statements [1] I took the action to 
> explore the way we currently do things like "link labels" [2] using the 
> recommended alternative of named graphs[3].  I'm sending this note out 
to 
> see if anyone else has any interesting insight on how this can be 
> accomplished.  I plan to send a note to the RDF WG as well.
> 
> To be honest, I struggle to find a clean way to do this with named 
graphs. 
>  Added to some of the challenges is how to define a simple PATCH format 
> that can be used to patch these reified statements.
> 
> Take for example this simple change request:
> @prefix ex: <http://example.com/bugtracker> .
> @prefix oslc: <http://open-services.net/ns/core#> .
> @prefix oslc_cm: <http://open-services.net/ns/cm#> .
> @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
> @prefix dcterms: <http://purl.org/dc/terms/> .
> 
> <http://example.com/bugs/2314>
>    a oslc_cm:ChangeRequest ;
>    oslc_cm:relatedChangeRequest <http://myserver/mycmapp/bugs/1235> ,
>       <http://remoteserver/mycmapp/defects/abc123> .
> 
> _:b1 
>         a rdf:Statement;
>         rdf:subject <http://example.com/bugs/2314>;
>         rdf:predicate oslc_cm:relatedChangeRequest;
>         rdf:object <http://myserver/mycmapp/bugs/1235>;
>         dcterms:title "My special link title".
> 
> So if I want to NOT use reified statements I'd have to model this 
> relationship a bit differently.  One idea would be to use a named graph 
> for the link statements. 
> The questions that need to be answered with this approach are:
> 
> 1. Simply how to form that graph and/or how to relate the graph with the 

> right "relationship" triple?
> 
> In thinking through this, it feels like I'm inventing reification and 
> doesn't seem like the desired outcome.  Let's try to force it for a 
moment 
> and say we can "compute" the graph name based on the relationship 
triple. 
> So for my example above, we have something horrible like (not encoding):
> Graph name = <
http://example.com/bugs/2314|http://open-services.net/ns/cm#
> relatedChangeRequest|http://myserver/mycmapp/bugs/1235>
> 
> 2. What is the subject of the triples within this new named graph?
> The subject and object of the relationship triple don't appear to be the 

> right choice.  Though, since we have this special private graph, perhaps 

> we can just use the object to pick one since we shouldn't have any 
> conflicts.
> 
> So the example becomes:
> 
> @prefix ex: <http://example.com/bugtracker> .
> @prefix oslc: <http://open-services.net/ns/core#> .
> @prefix oslc_cm: <http://open-services.net/ns/cm#> .
> @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
> @prefix dcterms: <http://purl.org/dc/terms/> .
> 
> <http://example.com/bugs/2314>
>    a oslc_cm:ChangeRequest ;
>    oslc_cm:relatedChangeRequest <http://myserver/mycmapp/bugs/1235> ,
>       <http://remoteserver/mycmapp/defects/abc123> .
> 
> :<http://example.com/bugs/2314|http://open-services.net/ns/cm#
> relatedChangeRequest|http://myserver/mycmapp/bugs/1235> = {
>    <http://myserver/mycmapp/bugs/1235> dcterms:title "My special link 
> title".     # This is a lie, not right subject
> }
> 
> This seems like a complete non-obvious abuse of this.   Hopefully 
someone 
> sees a more clear way to leverage named graphs and why I'm taking this 
> discussion to the mailing list.  If not, we can provide this feedback to 

> RDF WG and see if they have a proper solution or will justify keeping 
> reification or some subset.
> 
> [1] - http://www.w3.org/2011/rdf-wg/track/issues/25 , 
> http://open-services.net/pipermail/oslc-core_open-services.net/2012-
> February/001229.html
> [2] - 
> 
http://open-services.net/bin/view/Main/OslcCoreSpecAppendixLinks#2_Anchor
> [3] - 
> http://www.w3.org/TR/2012/WD-rdf11-concepts-20120605/#section-dataset
> 
> Thanks,
> Steve Speicher | IBM Rational Software | (919) 254-0645
> 
> 
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