Some comments on RDF Schema as RDF/XML

Some comments on RDF Schema as RDF/XML (Appendix A in RDF Schema Specification)

1. The definition of rdf:XMLLiteral 

<rdfs:Datatype rdf:about="http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral">
  <rdfs:isDefinedBy rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#"/>
  <rdfs:label>XMLLiteral</rdfs:label>
  <rdfs:comment>The class of XML literal values.</rdfs:comment>

   <!--Add an element to specify that rdf:XMLLiteral is a subclass of rdfs:Literal(section 2.5).-->
   <rdfs:subClassOf rdf:resource="http://www.w3.org/2000/01/rdf-schema#Literal"/>  

</rdfs:Datatype>

Although every instance of rdfs:Datatype is a subclass of rdfs:Literal (section 2.4, also rule rdfD 0c in section 4.3 of RDF Semantics Spec), we should also state that rdf:XMLLiteral is a subclass of rdfs:Literal because there is no simple way to represent the rule rdfD 0c in RDF/XML. 

2. The definition of rdfs:isDefinedBy 

<rdf:Property rdf:about="http://www.w3.org/2000/01/rdf-schema#isDefinedBy">
  <rdfs:isDefinedBy rdf:resource="http://www.w3.org/2000/01/rdf-schema#"/>

   <!--The following element is redundant, should be deleted. -->
  <rdf:type rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Property"/>

  <rdfs:subPropertyOf rdf:resource="http://www.w3.org/2000/01/rdf-schema#seeAlso"/>
  <rdfs:label>isDefinedBy</rdfs:label>
  <rdfs:comment>The defininition of the subject resource.</rdfs:comment>
  <rdfs:range rdf:resource="http://www.w3.org/2000/01/rdf-schema#Resource"/>
  <rdfs:domain rdf:resource="http://www.w3.org/2000/01/rdf-schema#Resource"/>
</rdf:Property>

3. The definitions of classes

Almost every class definition includes a rdfs:subClassOf element (some of them are trivial, such as specifying some class is an rdfs:subClassOf rdfs:Resource), except for the following:
rdfs:Resource,
rdfs:Literal,
rdfs:List,
rdf:XMLLiteral (See Point 1).

Alternatives: 
1) Specify rdfs:Literal and rdfs:List (even rdfs:Resource) be an rdfs:subClassOf rdfs:Resource. OR
2) Delete the element
  <rdfs:subClassOf rdf:resource="http://www.w3.org/2000/01/rdf-schema#Resource"/>
within the definitions of classes: rdfs:Class, rdf:Property, rdf:Statement, rdfs:Container.

As we know every class (including rdfs:Class and rdfs:Resource) is an rdfs:subClassOf rdfs:Resource, see section 2.1, or rule rdfs7a in section 4.2 of RDF Semantics Spec.

4. Uniformly ordering sub-elements to gain better readability

For the definitions of properties, sub-elements ordering could be as follows:
rdfs:isDefinedBy
rdfs:label
rdfs:comment
rdfs:domain
rdfs:range

For the definitions of classes, sub-elements ordering could be as follows:
rdfs:isDefinedBy
rdfs:label
rdfs:comment
rdfs:subClassOf 

End of my comments on RDF Schema as RDF/XML.


Thanks for your concern!


Yuzhong Qu
Dept. of Computer Science and Engineering
Southeast University, Nanjing 210096, P. R. China

Received on Tuesday, 11 February 2003 11:02:31 UTC