- From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
- Date: Fri, 22 Aug 2003 10:56:44 -0400 (EDT)
- To: www-rdf-comments@w3.org
The current version of the RDF Semantics document, titled RDF Semantics Editors Draft August 21, has continuing technical issues that I discovered in a quick, incomplete pass this morning. The document does not define ``character string'' or ``language tag''. These need precise definitions as the definition of simple interpretations depends on them. In the examples (in Section 1.4), the pictures do not correspond to the text, as they have Thing 1 in the domain whereas the text has 1 in the domain. The first picture also has the incorrect claim that ``The universe has just two things in it.'' The set of rdf-interpretations has changed significantly. An rdf-interpretation need not have domain elements corresponding to every possible XML literal. This does not affect RDF, but may be a problem for languages built on top of RDF. There are conditions imposed on the non-core RDF vocabulary by rdf-interpretations, counter to several claims in the document. The redundancy of ``all but one of the RDF axiomatic triples'' cannot be derived from ``the RDFS axiomatic triples and the smenatic conditions on rdfs:domain and rdfs:range''. It also requires the semantic condition for ICEXT to make these derivations. As well, the semantic conditions for rdfs:range are not needed. The definition of the Herbrand interpretation of a graph has all well-formed XML literals in LV, which is permissable, but incorrectly states that these are required to be in LV, and makes Herbrand interpretations non-minimal. It is not the case that a Herbrand interpretations is a simple interpretation - consider the Herbrand interpretation of the empty graph. As well, Herbrand interpretations abide by part of the RDF meaning of rdf:type, which also makes them non-minimal. The Herbrand lemma is false as Herbrand interpretations are non-minimal. The problems with Herbrand interpretations make the proof othe RDF entailment lemma and the RDFS entailment lemma suspect. The proof of the RDF entailment lemma is suspect in other ways, as the rdf-interpretation constructed (H') appears to have both XML values and blank nodes in the class extension of rdf:XMLLiteral. The details of XML literals are sufficiently arcane that I cannot determine whether this is permissable. On a minor note, the definition of proper instance means that <ex:a> <ex:b> "a" . is not a proper instance of <ex:a> <ex:b> _:xx . This affects the definition of lean graphs, and reduces the scope of the anonymity lemma. Peter F. Patel-Schneider
Received on Saturday, 23 August 2003 02:52:50 UTC