W3C home > Mailing lists > Public > semantic-web@w3.org > July 2012

Re: Why do we name nodes and not edges?

From: Hugh Glaser <hg@ecs.soton.ac.uk>
Date: Fri, 27 Jul 2012 11:47:02 +0000
To: Steve Harris <steve.harris@garlik.com>
CC: Austin William Wright <aaa@bzfx.net>, Melvin Carvalho <melvincarvalho@gmail.com>, Semantic Web <semantic-web@w3.org>
Message-ID: <E3E8144F-EA4F-43A2-8406-36452105E9A2@soton.ac.uk>

On 27 Jul 2012, at 09:37, 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.
I like this description.
I like using SemWeb technologies for the things that they are good at, which in my brain means it has to be easy.
People are welcome to think hard about how to push back the frontiers of what they might achieve, of course - that is research.
I think the platform that others have toiled over in the last decade has provided us with something that can be easily used with confidence.
But if some area is getting complex, than maybe it isn't the right technology.
Which of course means it could benefit from more toil, of course, such as provenance is doing.
Me? Clearly I'm just a parasite for others' toil.
> 
> - 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 11:52:26 UTC

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