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Some comments on the spec of RDF Semantics

From: Qu Yuzhong <yzqu@seu.edu.cn>
Date: Tue, 11 Feb 2003 23:57:51 +0800
Message-ID: <00ab01c2d1e6$557e0280$030f77ca@proxy.seu.edu.cn>
To: <www-rdf-comments@w3.org>
Cc: "RDF-Interest" <www-rdf-interest@w3.org>, <phayes@ai.uwf.edu>

Some comments on the spec of RDF Semantics:

A. The semantic conditions and axiomatic triples for rdfs-interpretation (section 3.3)

1) IC should contains I(rdf:XMLLiteral).
2) Add an axiomatic triple: rdf:XMLLiteral rdfs:subClassOf rdfs:Literal. Because the following semantic conditions could not guarantee that rdf:XMLLiteral is a subclass of rdfs:Literal:
ICEXT(I(rdfs:Literal)) is a subset of LV
ICEXT(I(rdf:XMLLiteral)) is the set of all canonical XML documents.
2') Another way is to require that
 ICEXT(I(rdf:XMLLiteral)) is a subset of ICEXT(I(rdfs:Literal)), such as by specifying that 
ICEXT(I(rdfs:Literal)) is a subset of LV, and includes all canonical XML documents and so on.


B. The rdfs-closure of an RDF graph 
The following is cited from section 4.2:
[[The rdfs-closure of an RDF graph E is the graph got by adding triples to E according to the RDF closure rules together with the following rules:
1. Add the RDFS axiomatic triples from the table in section 3.3, and all the following triples. There are many other triples which are true in every rdfs-interpretation, but they will be generated from these by the closure rules.

rdf:type rdfs:range rdfs:Class .

rdfs:Resource rdf:type rdfs:Class .
rdfs:Literal rdf:type rdfs:Class .
rdf:Statement rdf:type rdfs:Class .
rdf:nil rdf:type rdf:List .
rdf:XMLLiteral rdf:type rdfs:Datatype .

rdf:subject rdf:type rdf:Property .
rdf:predicate rdf:type rdf:Property .
rdf:object rdf:type rdf:Property .
rdf:first rdf:type rdf:Property .
rdf:rest rdf:type rdf:Property .

2. ...

3. ...

]]

The above eleven triples (except for: rdfs:Literal rdf:type rdfs:Class .) can also be gained or generated from the RDFS axiomatic triples in section 3.3 and the other closure rules. 
For example:
The following are gained from the RDFS axiomatic triples in section 3.3:
rdf:type rdfs:range rdfs:Class .
rdf:XMLLiteral rdf:type rdfs:Datatype .

The triple "rdf:nil rdf:type rdf:List ." is from the RDF closure rules (Point 1 of the section 4.1) 

The triple "rdf:subject rdf:type rdf:Property ." can be gained as follow: 
rdf:subject rdfs:domain rdf:Statement .(from the RDFS axiomatic triples in section 3.3)
rdfs:domain rdfs:domain rdf:Property .(from the RDFS axiomatic triples in section 3.3)
rdf:subject rdf:type rdf:Property . (the rule rdfs2)

Similar to others.

In addition, 
The triple "rdfs:Literal rdf:type rdfs:Class ." can also be generated if we add an axiomatic triple: rdf:XMLLiteral rdfs:subClassOf rdfs:Literal. as suggested in A.2).

In summary, 
1)there is no need to explicitly add the above eleven triples, 
2)but need to add: rdf:value rdf:type rdf:Property . 
3)The point 2 of section 4.2 seems to be redundant, these triples are from 
the RDFS axiomatic triples in section 3.3.


C. Typewriting error:
1) rdfRV (should be rdfV) in the first paragraph.
2) I(rdfs:comment) and I(rdfs:label) are repeated in the last row of the first table in section 3.3, as follows:

IP contains:
I(rdf:type), I(rdfs:domain), I(rdfs:range), I(rdfs:subPropertyOf), I(rdfs:subClassOf), I(rdfs:comment), I(rdfs:label), I(rdf:subject), I(rdf:predicate), I(rdf:object), I(rdfs:member), I(rdf:_1), I(rdf:_2), ... , I(rdf:first), I(rdf:rest), I(rdfs:seeAlso), I(rdfs:isDefinedBy), I(rdfs:comment), I(rdfs:label), I(rdf:value)



D. More like a question. Why not shift the rule rdfD 0c (section 4.3) to the category of the rdfs-closure rules(named as rdfs11)? 

The rule rdfD 0c means that every instance of rdfs:Datatype is a subclass of rdfs:Literal (also section 2.4 in the spec of RDF Schema). 

It seems reasonable to require the rdfs interpretation satisfying this constraint.


End of my comments on the spec of RDF Semantics.


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 11:01:19 GMT

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