Re: How does RDF get extended to new datatypes?

On Tue, Apr 23, 2013 at 10:09:31PM -0500, Pat Hayes wrote:
> Although RDF is usually treated as having its own special datatypes and the
> compatible XSD types as being the standard D, it is quite possible to use RDF
> with a larger D set, so that as new datatypes come along (eg geolocation
> datatypes, or time-interval datatypes, or physical unit datatypes, to mention
> three that I know have been suggested) and, presumably, get canonized by
> appropriate standards bodies (maybe not the W3C, though) for use by various
> communities, they can be smoothly incorporated into RDF data without a lot of
> fuss and without re-writing the RDF specs. 

Here's an example. DCMI declares twelve URIs as rdf:type rdfs:Datatype.  In
DCMI terminology, the following are URIs for "Syntax Encoding Schemes" [1].

    http://purl.org/dc/terms/Box
    http://purl.org/dc/terms/ISO3166
    http://purl.org/dc/terms/ISO639-2
    http://purl.org/dc/terms/ISO639-3
    http://purl.org/dc/terms/Period
    http://purl.org/dc/terms/Point
    http://purl.org/dc/terms/RFC1766
    http://purl.org/dc/terms/RFC3066
    http://purl.org/dc/terms/RFC4646
    http://purl.org/dc/terms/RFC5646
    http://purl.org/dc/terms/URI
    http://purl.org/dc/terms/W3CDTF

ISO3166, for example, is defined as "The set of codes listed in ISO 3166-1 for
the representation of names of countries."

Most of these twelve URIs date from 2000 [2]. The ones coined after 2000 were
for updated versions of the ISO and RFC specifications. If I correctly recall,
the idea of saying that these are RDFS datatypes was first proposed in circa
2002 by Eric Miller.  In the mid 2000s, the DCMI Usage Board reviewed all of
the existing "encoding schemes" [3] to decide whether they represented
Vocabulary Encoding Schemes (which are something like SKOS Concept Schemes,
only without necessarily being expressed in SKOS or having URIs for individual
terms) or Syntax Encoding Schemes (the twelves listed above).

At the time, we interpreted the ISO 3166 specification, for example, as 
representing a lexical space (e.g., "AS", "AU"...), a value space ("American
Samoa", "Australia"...), and a lexical-to-value mapping ("AS" = "American 
Samoa", as specified in [4]).

Tom

[1] http://dublincore.org/documents/dcmi-terms/#H5
[2] http://dublincore.org/documents/2000/07/11/dcmes-qualifiers/
[3] http://dublincore.org/usage/documents/principles/#encoding-scheme
[4] http://www.iso.org/iso/en/prods-services/iso3166ma/02iso-3166-code-lists/list-en1.html

-- 
Tom Baker <tom@tombaker.org>

Received on Friday, 26 April 2013 15:35:38 UTC