W3C home > Mailing lists > Public > public-data-shapes-wg@w3.org > January 2015

Re: Shapes vs Classes (in LDOM)

From: Arthur Ryman <ryman@ca.ibm.com>
Date: Thu, 29 Jan 2015 11:53:15 -0500
To: RDF Data Shapes Working Group <public-data-shapes-wg@w3.org>
Message-ID: <OF9116E200.D68406D5-ON85257DDC.005AAEF7-85257DDC.005CC524@ca.ibm.com>
Holger Knublauch <holger@topquadrant.com> wrote on 01/24/2015 07:53:45 PM:
> To me the only 
> remaining question is whether users would find it more "clean" or 
> "intuitive" to have a special term "shape" for what is essentially the 
> same thing as "class". 

I disagree that "shape" is essentially the same thing as "class". I can 
see your point if we are talking about OO data types. However, the 
situation with RDF is very different.

In RDF, "class" is used to classify resources. Given a resource, it's 
either in the class or not in the class. So a class defines a set of 
resources. The classification may be explicit via the presence of an 
rdf:type triple, or it may be inferred via RDFS or OWL.

In contrast, a "shape" describes constraints on RDF graphs, i.e. sets of 
triples. There is no requirement that an RDF graph contain rdf:type 
triples. It may contain zero or more.

In practice, many RDF graphs do arise from OO data types. That is an 
important pattern, so we should make it easy to describe. However, we 
shouldn't exclude the general case which is also valuable and is one of 
the motives for using RDF instead of alternatives.

-- Arthur Ryman
Received on Thursday, 29 January 2015 16:53:55 UTC

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