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Re: RDF Semantics: presenting the definition of rdfs interpretations

From: pat hayes <phayes@ai.uwf.edu>
Date: Sun, 13 Apr 2003 16:14:58 -0500
Message-Id: <p05111b02babf82122d1b@[10.0.100.6]>
To: herman.ter.horst@philips.com
Cc: www-rdf-comments@w3.org

Herman, while doing a hopefully close-to-final edit of the semantics 
document, and bearing in mind your concerns about the initial 
presentation of the material on rdfs interpretations in section 3.3, 
I now propose to simplify the introductory prose so as to avoid the 
misleading impression of giving duplicate definitions, and to clarify 
the point raised in your recent message, as follows.  Please let me 
know if you would find this acceptable.

Pat

--------

3.3 RDFS Interpretations

RDFSchema extends RDF to include a larger vocabulary rdfsV with more 
complex semantic constraints:

RDFS vocabulary (table)
rdfs:domain rdfs:range rdfs:Resource rdfs:Literal rdfs:Datatype 
rdfs:Class rdfs:subClassOf rdfs:subPropertyOf rdfs:member 
rdfs:Container rdfs:ContainerMembershipProperty rdfs:comment 
rdfs:seeAlso, rdfs:isDefinedBy rdfs:label

(rdfs:comment, rdfs:seeAlso, rdfs:isDefinedBy and rdfs:label are 
included here because some constraints which apply to their use can 
be stated using rdfs:domain, rdfs:range and rdfs:subPropertyOf. Other 
than this, the formal semantics does not assign them any particular 
meanings.)

Although not strictly necessary, it is convenient to state the RDFS 
semantics in terms of a new semantic construct, a 'class', i.e. a 
resource which represents a set of things in the universe which all 
have that class as the value of their rdf:type property. Classes are 
defined to be things of type rdfs:Class, and the set of all classes 
in an interpretation will be called IC. The semantic conditions are 
stated in terms of a mapping ICEXT (for the Class Extension in I) 
from classes to their extensions. The meanings of ICEXT and IC in a 
rdf-interpretation of the RDFS vocabulary are completely defined by 
the first two conditions in the table below. Notice that a class may 
have an empty class extension; that (as noted earlier) two different 
class entities could have the same class extension; and that the 
class extension of rdfs:Class contains the class rdfs:Class.

An rdfs-interpretation of V is an rdf-interpretation I of (V union 
rdfV union rdfsV) which satisfies the following semantic conditions 
and all the triples in the subsequent table, called the RDFS 
axiomatic triples.

(table)
x is in ICEXT(y) iff <x,y> is in IEXT(I(rdf:type))

IC = ICEXT(I(rdfs:Class))
.....



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Received on Sunday, 13 April 2003 17:15:01 GMT

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