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Re: Data Model Assumptions

From: Raphaël Troncy <raphael.troncy@eurecom.fr>
Date: Tue, 18 Aug 2015 15:34:03 +0200
To: Ivan Herman <ivan@w3.org>, Doug Schepers <schepers@w3.org>
Cc: W3C Public Annotation List <public-annotation@w3.org>
Message-ID: <55D3344B.40500@eurecom.fr>
Dear all,

I would do a +1 for the very good set of precisions brought by Ivan, I 
concur to everything which is said in this message. I would bring the 
following clarification note:

>> * unusual, but apparently optional, "predicate" names (e.g. "hasBody")
>
> That is not part of any kind of any RDF standard, it is just the habits that a particular community has (often inherited from people who defined vocabularies, library catalogues, etc, way before even the Web existed).

The RDF data model results in a DAG (Directed Acyclic Graph). This means 
that the predicates are directed (in your image representation, you have 
a left side and a right side of the arrow). RDF does not say more than this.

As Ivan pointed out, in practice, some people felt that this "direction" 
of the predicate should be conveyed in the predicate name, thus the 
pattern you encounter under the form "hasXXX" or "isXXXBy" and that 
apparently you found "unusual" or even perhaps "awkward".

Now, let's imagine that you encounter the predicate name "broader", and 
more precisely, the statement "x broader y" ... do you know if x is 
broader than y or if this is the over way around? You may want to ask 
SKOS that has an opinion on this [1]. The truth is that if you ask the 
developers(*), you will get 20% of the people that think this is one 
way, 20% that thinks this is the other way and 60% that just think this 
was a terrible predicate name since they have to systematically look at 
the spec [1]! I'm not saying that the hasXXX pattern should always been 
used, I'm just trying to explain you where it comes from ... releasing 
the ambiguity that "some" predicate names naturally have when providing 
a cue of their direction.

Best regards.

   Raphaël

(*) Very informal but still serious poll among the many debates that 
took place when implementing the SKOS specification.

[1] http://www.w3.org/TR/skos-reference/#broader

-- 
Raphaël Troncy
EURECOM, Campus SophiaTech
Multimedia Communications Department
450 route des Chappes, 06410 Biot, France.
e-mail: raphael.troncy@eurecom.fr & raphael.troncy@gmail.com
Tel: +33 (0)4 - 9300 8242
Fax: +33 (0)4 - 9000 8200
Web: http://www.eurecom.fr/~troncy/
Received on Tuesday, 18 August 2015 13:34:33 UTC

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