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Re: Terminology: How to call "IRI or blank node"?

From: Holger Knublauch <holger@topquadrant.com>
Date: Sat, 10 Jan 2015 08:52:12 +1000
Message-ID: <54B05B9C.3050002@topquadrant.com>
To: "public-data-shapes-wg@w3.org" <public-data-shapes-wg@w3.org>
On 1/9/15, 12:40 PM, Peter F. Patel-Schneider wrote:
>
> This is absolutely counter to the requirement that the working group 
> must use rdfs:Resource in a way that abides by its meaning as defined 
> in the RDF specification.

Peter,

I think the situation is not as clear-cut. Using rdfs:Resource in the 
context of :valueType would IMHO be perfectly fine with the RDF 
specification.

Look at rdfs:domain for example. The triple

     ex:property rdfs:domain rdfs:Resource

means that the domain of ex:property is IRIs or blank nodes - literals 
are excluded because there is *another* rule in RDF which disallows 
literals to appear as subjects in RDF triples. All these semantic rules 
are conjoined. In the same spirit, I see no reason why we cannot add an 
additional rule that in the context of :valueType, the meaning is 
narrowed down to IRIs or blank nodes. As long as we only narrow down the 
value space, this is IMHO perfectly fine.

Another example is

     ex:property rdfs:range rdfs:Literal

According to the RDF Schema spec,

"The class rdfs:Literal is the class of literal values such as strings 
and integers. Property values such as textual strings are examples of 
RDF literals."

Well, this is quite ambiguous. Does this mean that the following is in 
the range?

     ex:MyLiteral a rdfs:Literal .
     ex:MySubject ex:property ex:MyLiteral .

I guess not, because otherwise almost every existing RDF processor is 
wrong. However, how can rdfs:Literal then be a class, if it cannot 
really have meaningful instances? So apparently, rdfs:Literal is 
interpreted differently when it is used in the context of rdfs:range.

Finally, let's not forget that - in addition to remaining as compatible 
as possible to the existing specs - this WG works in unchartered 
territory in which many original RDF design decisions such as the open 
world assumption are no longer valid. Furthermore, the group also has 
the goal to create a user-friendly and intuitive language. The fact that 
the vast majority of users find the current interpretations of 
rdfs:Resource confusing should encourage us to think outside of the box.

Regards,
Holger
Received on Friday, 9 January 2015 22:52:45 UTC

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