From: Pat Hayes (phayes@ai.uwf.edu)
Date: 10/04/01
>Hi: > >Here is a little document that I prepared. It takes (most) of the datatype >ideas from DAML+OIL (March 2001) and recasts them informally as an >extension to RDF Schema. > >Now for the political part: > >1/ I think it would be better if this were to come from the > joint committee. Can we discuss this at the next meeting and adopt it > (or not)? > >2/ Things are moving fast on the RDF front, so if the joint committee can't > make a decision soon, I may have to unilaterally reluctantly decide to > push it out from just me. > >3/ Where should this go? I'm almost of the opinion that it should go to > the Semantic Web coordination group instead of the RDF Core Working > Group. > >Comments, please. > >peter > > > > > > Adding Datatypes to RDF Schema > > Peter F. Patel-Schneider > > >Here is a method for adding datatypes to RDF Schema that fits well >with what I see as the RDF Schema philosophy. > > >INTRODUCTION > > >First some desiderata: > >1/ The datatype scheme should be backward compatible with RDF and RDF > Schema as they are currently constituted. > > From this, I get that the following n-triples should still be allowed: > > John age "5" . > John streetAddress "12a" . > Mary streetAddress "5" . > >2/ The datatype scheme should allow type information to be specified in the > same way that RDF Schema provides ``type'' information for resources. This suggests a problem to me, since this kind of typing is inherently subject to inference; it can't be checked by a parser. Isn't that the whole point of having literals in the first place, that you can determine their identity (and some of their properties, eg length of strings, value of numerals) just by looking at them? Unlike logical constants, they aren't replaceable by gensyms. There ought to be some way in which the typing information for literals is distinguishable from general rdf:type assertions, so that it can be picked out by a processor in one scan of a document or graph on purely syntactic grounds. That may be compatible with your suggestion below, but I'd like to see it made explicit. > From this, I get that the following is a (or, perhaps, the) way to > specify the type of a literal: > > Mary age "07" . > age rdfs:range ????:integer . > John age "05" . > > >THE PROPOSAL > > >The basic idea of the proposal is quite simple. > >1/ Change the value space for literals from an uninterpreted > quasi-character space to the disjoint union of a collection of value > spaces. > >2/ Allow untyped literals to denote any element of this value space for > which they are lexical representations. > >3/ Use special URIs to refer to these value spaces and incorporate their > meaning into the meaning of RDF Schema. How does this differ from the proposal that Patrick Stickler has been outlining on rdf-logic? >For technical details on one way to do something very close to this, see >the model theory for DAML+OIL at > http://www.daml.org/2001/03/model-theoretic-semantics.html > > >What sort of URIs and value spaces could be used? Just about any kind. >Primitive XML Schema datatypes would work and will be used in the following >examples. The mechanism can be extended to all XML Schema datatypes and >with some extensions probably even to all of XML Schema. > > >EXAMPLES AND COMMENTARY > > >A n-triple example using XML Schema datatypes: > > > John age "5" . > >All that is known so far is that John's age is some data value that can be >lexicalized as 5. > > John streetAddress "05" . > Mary streetAddress "5" . > >It is not know yet whether John's age is the same data value as Mary's >street address. Also John and Mary could turn out to have the same >streetAddress > > John age "05" . > >It is not known yet whether John has two ages. > > age rdfs:range xsd:integer . > >Now we know that the two statements about John's age denote the same >information. > > streetAddress rdfs:range xsd:string . > >Now we know that John's street address is different from Mary's street >address. > > >An RDF/XML version of more-or-less the above example: > ><rdf:RDF> > >.... > ><rdf:Property rdf:ID="streetAddress"> > <rdfs:range rdf:resource="xsd:string" /> ></rdf:Property> > ><Person rdf:ID="John"> > <age>5</age> > <streetAddress>05</streetAddress> ></Person> > ><Person rdf:ID="Mary"> > <streetAddress>5</streetAddress> ></Person> > ><Person rdf:about="John"> > <age>05</age> ></Person> > >.... > ><rdf:Property rdf:ID="age"> > <rdfs:range rdf:resource="xsd:integer" /> ></rdf:Property> > ></rdf:RDF> That does look very pretty, I agree. Pat -- --------------------------------------------------------------------- IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola, FL 32501 (850)202 4440 fax phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
This archive was generated by hypermail 2.1.4 : 04/02/02 EST