Re: How does RDF get extended to new datatypes?

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