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

On 12/22/2014 01:45 AM, ☮ elf Pavlik ☮ wrote:
> On 12/21/2014 01:38 AM, Peter F. Patel-Schneider wrote:
>> In RDF all resources can have property values, even literal values.
>>
>> peter
> Hi Peter :)
>
> Could you please explain it little more and if possible share links to
> relevant references?
>
> Thanks!
>
>

The original version of RDF, as described in the RDF Model and Syntax 
Specification http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/, talks about 
Resources and Literals, but does not indicate directly whether they are 
disjoint.  However, there is already the idea that anything is a resource and 
that anything can described by a URI.  See Section 2
http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/#basic and Section 5 
http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/#model for more information.

The original version of RDFS, http://www.w3.org/TR/1998/WD-rdf-schema/, which 
never became a full W3C recommendation, has the initial class hierarchy, 
including rdfs:Resource, rdfs:Literal, rdfs:Class, and rdf:Property in Figure 
2.   In this figure, rdfs:Resource is the universal class, with rdfs:Class, 
rdf:Property, and rdfs:Literal all as subclasses.  Here is the first direct 
requirement that literal values are resources.

The first formal treatment of RDF is in RDF Semantics 
http://www.w3.org/TR/2004/REC-rdf-mt-20040210/.  Here interpretations for RDF 
are first defined, in Section 1.3 
http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#interp, with the domain of an 
interpretation being the set of resources and a subset of the resources being 
literal values, as in the original version of RDFS.  Properties are another 
subset of the resources, which are linked to their extent, which is a set of 
pairs over the resources.  There is no requirement here that literals cannot 
be the first element of a property pair.


One might argue that the formal treatment is a misreading of the informal 1999 
description of RDF, but the ability for literals to have property values has 
definitely been in RDF since at least 2004.  This stance is also consistent 
with the dictum that URIs can identify anything, which includes literal values.

For example, one can say in RDF

ex:two rdf:type xsd:Integer .
ex:two ex:prime xsd:true .


Peter F. Patel-Schneider
Nuance Communications

Received on Monday, 22 December 2014 13:50:10 UTC