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Re: Why do we name nodes and not edges?

From: Hugh Glaser <hg@ecs.soton.ac.uk>
Date: Thu, 26 Jul 2012 10:17:41 +0000
To: Danny Ayers <danny.ayers@gmail.com>
CC: Melvin Carvalho <melvincarvalho@gmail.com>, Steve Harris <steve.harris@garlik.com>, Dave Reynolds <dave.e.reynolds@gmail.com>, "<semantic-web@w3.org>" <semantic-web@w3.org>
Message-ID: <86B1556B-BFFA-4401-BB13-7DDD985E22EA@soton.ac.uk>
Thanks guys.
These messages are a bright spot in my otherwise dull existence.

On 26 Jul 2012, at 10:05, Danny Ayers <danny.ayers@gmail.com>
 wrote:

> Tractability. Having the predicate/property bits shared (comparable to
> static classes) means any reasoning you want to do over them gets
> easier (I'm not sure, but flexible predicates probably means flipping
> beyond FOL).
> 
> Pragmatically, if you have a different URI in the middle, how are you
> going to query against it?
By having "Classes" of URIs in the middle, indicated by subProperty, in the same way as for the URIs at the ends indicated by subClass?

If you encode more information in the URI in the middle you can have more general URIs at the ends.
At the moment we make the end ones very specific and the middle ones very generic.
No reason why we can't have middle ones saying :car-owned-by-steve.
I am guessing that by specifying stuff about the end URIs would allow various inferences to be made about middle URIs, just as specifying stuff about properties allows inferences to be made about end URIs.
I think you would probably lose the distinction between Instance and Class for end URIs, which seems to float around for some reason. What we are talking about is sort of introducing Instances for middle URIs?

Do we not have Duals here, and both could be used at the same time?
I think I may need to duck back into my Linked Data box now, and batten down the hatch :-)

Cheers
Hugh
> 
> Cheers,
> Danny.
> 
> On 25 July 2012 18:11, Melvin Carvalho <melvincarvalho@gmail.com> wrote:
>> 
>> 
>> On 25 July 2012 18:08, Steve Harris <steve.harris@garlik.com> wrote:
>>> 
>>> Yes, exactly, I was writing in a bit of a hurry, maybe a UUID would make
>>> made it clearer.
>> 
>> 
>> Thanks for the responses, is there a standard way to encode
>> 
>> "triple"
>> 
>> into
>> 
>> urn:uuid:triple?
>> 
>> (For the sake of convenience, let's assume we are not dealing with bnodes)
>> 
>>> 
>>> 
>>> - Steve
>>> 
>>> On 2012-07-25, at 17:04, Dave Reynolds wrote:
>>> 
>>>> If I understand Steve's point he was meaning that you can mint a new
>>>> unique edge:xxxxxx identifier for each edge.
>>>> 
>>>> [Presumably you could make that a subPropertyOf the actual property you
>>>> wanted to assert.]
>>>> 
>>>> Cheers,
>>>> Dave
>>>> 
>>>> On 25/07/12 16:47, Aidan Hogan wrote:
>>>>> Steve,
>>>>> 
>>>>> If I understand Melvin's point, in RDF, edge:123456 is the URI of a
>>>>> property used to label the edge, not the edge itself.
>>>>> 
>>>>> Analogously, you don't identify a class-instance by it's class URI.
>>>>> 
>>>>> An edge is between two things. It might be directed and it might be
>>>>> labelled. In RDF it's both.
>>>>> 
>>>>> Hence, the edge would encapsulate the full triple, including source
>>>>> (subject) and target (object) nodes, as well as the label (predicate).
>>>>> 
>>>>> Cheers,
>>>>> Aidan
>>>>> 
>>>>> On 25/07/2012 16:18, Steve Harris wrote:
>>>>>> Nothing stops you from giving edges a unique URI, infact I think I've
>>>>>> worked on systems that did that.
>>>>>> 
>>>>>> e.g.
>>>>>> 
>>>>>> <foo> <http://example.com/edge/123456> 1 .
>>>>>> <http://example.com/edge/123456> a rdf:Property .
>>>>>> ...
>>>>>> 
>>>>>> - Steve
>>>>>> 
>>>>>> On 2012-07-25, at 16:07, Melvin Carvalho 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/
>>>>>> Registered in England and Wales 653331 VAT # 887 1335 93
>>>>>> Registered office: Landmark House, Experian Way, Nottingham, Notts,
>>>>>> NG80 1ZZ
>>>>>> 
>>>>> 
>>>>> 
>>>> 
>>>> 
>>> 
>>> --
>>> Steve Harris, CTO
>>> Garlik, a part of Experian
>>> +44 7854 417 874  http://www.garlik.com/
>>> Registered in England and Wales 653331 VAT # 887 1335 93
>>> Registered office: Landmark House, Experian Way, Nottingham, Notts, NG80
>>> 1ZZ
>>> 
>>> 
>> 
> 
> 
> 
> -- 
> http://dannyayers.com
> 
> http://webbeep.it  - text to tones and back again
> 
Received on Thursday, 26 July 2012 10:18:24 UTC

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