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Re: Why do we name nodes and not edges?

From: Austin William Wright <aaa@bzfx.net>
Date: Fri, 27 Jul 2012 04:29:12 -0700
Message-ID: <CANkuk-UdswkPOTXOTHJ_pXoMDmfvztbTYYOSM4JrGsN2QHXFoA@mail.gmail.com>
To: Steve Harris <steve.harris@garlik.com>
Cc: Melvin Carvalho <melvincarvalho@gmail.com>, Semantic Web <semantic-web@w3.org>
The important point is that you *can* talk about specific edges, as
resources. (How else would you do it?) It might seem awkward (seeing as
it quadruples the size of your database), but you don't even need RDF
Reification as such, if the database can natively assign an identifier to
each statement/edge. The concept isn't that much different than named
graphs/quads, with the additional constraint there may only be one RDF
statement per graph.

Whenever when you're getting into manipulating metadata, making statements
about statements, you're going to get into unique problems no matter how
you work with it.

Austin Wright.

On Fri, Jul 27, 2012 at 1:37 AM, Steve Harris <steve.harris@garlik.com>wrote:

> 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
> Garlik, a part of Experian
> +44 7854 417 874  http://www.garlik.com/
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> 1ZZ
Received on Friday, 27 July 2012 11:29:46 UTC

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