Re: proposed changes to the rdf:text document for option 5

From: Jonathan Rees <jar@creativecommons.org>
Subject: Re: proposed changes to the rdf:text document for option 5
Date: Wed, 27 May 2009 16:24:05 -0500

> On Wed, May 27, 2009 at 11:26 AM, Peter F.Patel-Schneider
> <pfps@research.bell-labs.com> wrote:
>>
>> [Changes to two last paragraphs of Section 1]
>>
>> To address these deficiencies, this specification introduces a datatype
>> called rdf:text, which uses the rdf: prefix because it refers to parts
>> of the conceptual model of RDF.  This extension, however, does not
>> change the conceptual model of RDF, and thus does not affect the
>> specifications that depend on the conceptual model of RDF such as
>> SPARQL.  The value space of rdf:text consists of all data values
>> assigned to RDF plain literals, which allows RDF applications to
>> explicitly refer to this set (e.g., in rdfs:range assertions).
>>
>> Because RDF plain literals are already a part of RDF and SPARQL
>> syntaxes, rdf:text literals are always written as RDF plain literals in
>> RDF and SPARQL syntaxes.
> 
> "literals are written as literals" is a use/mention confusion; a
> literal can't be written
> as a different literal, because it is already written. You're really
> talking about how the
> values are written. 

This is RDF.  Check your assumptions at the door.

Literals in RDF graphs (the data model of RDF) are indeed written as
literals in RDF surface syntaxes (e.g., RDF/XML and Turtle).  Already in
RDF some typed literals in RDF graphs are not written as typed literals
of the surface syntax.  A particularly interesting example is typed
literals with datatype rdf:XMLLiteral, which are written as XML Literals.

> How about:
>   Because the syntaxes of RDF and SPARQL already provide a way to
>   write these values, they are always written using plain literals in
> RDF and SPARQL,
>   not as typed literals with type rdf:type_formerly_known_as_rdf_text.

But this is not what I wanted to say at all.  This has the effect that
you can't use xsd:string in RDF syntaxes.

I could have been more precise, saying something like

  typed literals with datatype URI rdf:type_formerly_known_as_rdf_text
  in RDF graphs are always written as plain literals in linear and
  exchange syntaxes for RDF (including but not limited to RDF/XML and
  Turtle) 

Perhaps this is going to be the required wording, but it does have to be
very carefully crafted to cover no more and no less than needed.

Peter F. Patel-Schneider
Bell Labs Research

Received on Thursday, 28 May 2009 00:05:43 UTC