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Re: Why do we name nodes and not edges?

From: Steve Harris <steve.harris@garlik.com>
Date: Fri, 27 Jul 2012 09:37:43 +0100
Cc: Melvin Carvalho <melvincarvalho@gmail.com>, Semantic Web <semantic-web@w3.org>
Message-Id: <94678457-AB09-4409-A944-C8068BBBB5CB@garlik.com>
To: Austin William Wright <aaa@bzfx.net>
Yeah, but that example uses reification, which is at best frowned upon.

Increasingly my reaction to these kinds of questions is: maybe you shouldn't be using RDF.

RDF has limits of expressivity, [all IMHO] it's best for describing things in a way that the descriptions can easily be consumed by other reasonably generic processors - once you start delving off into obscure corners - e.g. something that was said by person X, believed by person Y, but not person Z, and then published by W - then you're no longer in the territory of easily. Even once you've somehow parsed that lot, doing anything useful with it - in an even vaguely generic way - is beyond complex.

- Steve

On 2012-07-26, at 16:30, Austin William Wright wrote:

> At least in RDF, resources (the node of the graph) are first class citizens.. You can describe edges as resources, you just need give the resource an identifier first:
> <triple1234>
>     a rdf:Statement ;
>     rdf:subject <foo> ;
>     rdf:predicate <http://example.com/edge/123456> ;
>     rdf:object 1 .
> Since edges/RDF statements with the same subject, predicate, and object must be the same edge, this identifies edges. Any rdf:Statement resources with the same values for subject, predicate, object, would be different URIs for the same resource.
> We don't see this more often because usually edges aren't resources "of significance", there's not much reason to describe specific facts. Generally, people make statements on entire graphs of RDF statements, the graph getting a URI. These don't usually get stored themselves as RDF statements for practical database reasons, but you could, as an RDF Collection of rdf:Statement resources.
> Austin Wright.
> On Wed, Jul 25, 2012 at 8:07 AM, Melvin Carvalho <melvincarvalho@gmail.com> wrote:
> Sorry if this topic has been covered before, but I have a question based on the axioms of the web, in particular:
> Axiom 0a: Universality 2    Any resource of significance should be given a URI.
> In this case we consider the web to be a directed graph (of nodes and edges), where a node corresponds to a resource but edge does not.
> We are encouraged to make nodes universal by giving them a URI.
> Why dont edges get the same treatment, ie encouragment to give it a (universal) name.  Is it even practical?
> I know there's such thing as reification but that seems to be unpopular (maybe before my time).
> I'm just curious as to whether this seems asymmetrical, that nodes are seemigly treated in one way, and edges in another?

Steve Harris, CTO
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Received on Friday, 27 July 2012 08:38:18 UTC

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