- From: Sandro Hawke <sandro@w3.org>
- Date: Sun, 28 Apr 2013 16:52:30 -0400
- To: Thomas Baker <tom@tombaker.org>
- CC: Pat Hayes <phayes@ihmc.us>, W3C RDF WG <public-rdf-wg@w3.org>
On 04/26/2013 11:35 AM, Thomas Baker wrote: > 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]). Interesting. Kind of an aside: why use datatypes instead of just properties? Has it turned out to be better this way? My understanding is that in RDF modeling, when you have an (inverse-functional) mapping from something to strings, you have to choose whether to call it a datatype or just have it be a property. My sense is that the only good time to make it a new datatype is if you're going to have hardcoded software support for it, as in many SPARQL engines. But maybe there's some other reason to use datatypes....? -- Sandro > 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 >
Received on Sunday, 28 April 2013 20:52:43 UTC