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

Re: Well Behaved RDF - Taming Blank Nodes, etc.

From: Atila <atilaromero@gmail.com>
Date: Thu, 20 Dec 2012 08:44:31 -0200
Message-ID: <50D2EC0F.7010004@gmail.com>
CC: Semantic Web <semantic-web@w3.org>
On 19-12-2012 12:45, Lee Feigenbaum wrote:
> On 12/19/2012 7:53 AM, Atila wrote:
>> On 18-12-2012 15:11, Lee Feigenbaum wrote:
>>> For the latter, I'd probably just model it as :Jane :wants :Apple or 
>>> something like that.
>> Hum, and if she wants a green apple, like
>>
>> :Jane :wants [a :Apple; :color :Green]
>>
>> ?
>
> Well, if my intuition is right that
>
> :Jane :wants [a :Apple]
>
> is incorrect modeling for "Janes (notionally) wants an apple", then 
> the above is similarly incorrect for Jane (notionally) wanting a green 
> apple, and instead I'd suggest:
>
> :Jane :wants :GreenApple .
> :GreenApple rdfs:subClassOf :Apple ; rdfs:subClassOf [ a 
> owl:Restriction ; owl:onProperty :color ; owl:hasValue :Green ] .
>
> (oh look, a blank node! :-) )
>
>> I think that the botton line is that machines doesn't need blank 
>> nodes at all, they can work very well without it. But humans do.
>> It is possible to express things using URIs to everthing, but it is 
>> just too messy in some cases. It would be painful, specially to 
>> beginners.
>
> Blank nodes are subtle and non-obvious (see the above discussion). I 
> disagree that they're simpler for beginners. I think beginners would 
> have an easier way getting started without them.
>
>> When i first heard about RDF, I got scared that every single thing 
>> would got to have an URI. I thought "that can describe social 
>> networks well, but will be useless to NLP", then I heard about blank 
>> nodes and saw I was wrong.
>>
>
> We do NLP all the time and everything gets a URI.
>
> Lee
>
>
But doesn't it get too verbose?

It is possible to rewrite your GreenApple suggestion without the blank 
node, but I think it would become more difficult to read, at least to 
me. And that is just one Restriction, imagine how would be to learn 
Restrictions without blank nodes. The remaining students would flee!
I'm just pointing that, among other things, bNodes offer syntactic 
sugar, which is an human thing.

About the example, I'm not sure about what Jane wants. Is it every green 
apple in the world an object of her desire? Or does she wants an 
specific apple that we don't know nothing but its color? That itself 
could lead to another discussion, which is not goal.
I think the important thing here is that there are people very attached 
to their bNodes (me included), and don't want to let they go. So please 
don't ban bNodes tomorrow, that could put an end to the world.
Received on Thursday, 20 December 2012 10:44:56 UTC

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