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Are rdfs:range and rdfs:domain really constraints?

From: Jan Algermissen <jalgermissen@topicmapping.com>
Date: Tue, 30 May 2006 21:25:02 +0200
Message-Id: <E0033CC6-B994-44BA-9224-F7102DA434EB@topicmapping.com>
To: semantic-web@w3.org


DCMI has today published a new draft on how to use DC with RDF[1].


"6. Using domains and ranges

RDF supports using "domain" and "range" constraints on RDF  
properties, for limiting the kinds of resources that a property apply  
to, and the kinds of resources that may occur as values,  
respectively. This is not currently part of the DCMI Abstract Model.  
However, some properties may still come with such constraints,  
expressed formally in RDF schemas or informally in accompanying  
documentation. It is strongly recommended that metadata implementors  
be careful to follow such contraints when they exist, to ensure  
maximum interoperability. This is even more important in RDF than in  
other expressions of Dublin Core, as RDF adds a well-defined model  
for automatic processing of domain and range contraints."

I would think that the above paragraph reveals a deep  
misunderstanding about the nature of rdfs:range and rdfs:domain (and  
the purely descriptive nature of RDF in general), is that correct?

My reading has allways been that RDF is purely descriptive and that  
there is no possibility to express the kinds of contraints mentioned  
in the quoted paragraph: that only instances of *certain* classes may  
occurr as subjects or objects of statements with a certain property.

So, if I say that foo:employer rdfs:range foo:company the I say that  
every resource that happens to be the object of a foo:employer  
statement is a foo:company but I do not say that only (see 'may' in  
quote) foo:company instances may be objects fo such statements.

Therefore, I don't understand what interoperability benefit  
rdfs:range and rdfs:domain can bring...since they do not license any  
assumptions about the data exchanged.

Can someone clarify if I am right or wrong or what?


Received on Tuesday, 30 May 2006 19:25:37 UTC

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