RE: text "MUST replace in the graph"

Hello,

This part of the text has been introduced to address the compatibility problems
pointed out by the HP people.

Furthermore, I'm not really sure I understand this comment. Please note the
following things:

- This requirement pertains *only* to RDF graph exchange and says *nothing*
about other types of formats. For example, the OWL 2 functional-style syntax
permits rdf:text literals without any problems; similarly, there is nothing that
prevents RIF from allowing rdf:text literals to occur in non-RDF exchange
formats.

- RDF plain literals "abc" and "abc"@lang are fully equivalent to typed rdf:text
literals "abc@"^^rdf:text and "abc@lang"^^rdf:text, respectively. Thus, even if
MUST is left as it is, nothing is lost from the expressivity point of view: this
requirement merely means that all typed rdf:text literals MUST be canonicalized
to (equivalent) plain RDF literals. Since the two are equivalent, there is no
loss of functionality. For example, if you want to exchange ground facts between
RIF implementations using RDF, you can do so as long you use the (equivalent)
plain RDF literal forms rather than the typed rdf:text literal ones. The RIF
implementation that sends the RDF graph can thus send all the data without any
loss of information, and the RIF implementation that receives the RDF graph can
reconstruct the original graph up to logical equivalence.

Regards,

	Boris

> -----Original Message-----
> From: public-rdf-text-request@w3.org [mailto:public-rdf-text-request@w3.org]
> On Behalf Of Sandro Hawke
> Sent: 06 April 2009 18:02
> To: public-rdf-text@w3.org
> Subject: rdf:text "MUST replace in the graph"
> 
> 
> (This is my second substantive comment in my rdf:text review; so far all
> my other comments are editorial, and I'll send them along separately.)
> 
> I don't think the text at the end of section 4 is quite right.  It
> currently says:
> 
>      Despite the semantic equivalence between typed rdf:text RDF
>      literals and plain RDF literals, the presence of typed rdf:text RDF
>      literals in an RDF graph might cause interoperability problems
>      between RDF tools, as not all RDF tools will support
>      rdf:text. Therefore, before exchanging an RDF graph with other RDF
>      tools, an RDF tool that suports rdf:text MUST replace in the graph
>      each typed rdf:text RDF literal with the corresponding plain RDF
>      literal. The notion of graph exchange includes, but is not limited
>      to, the process of serializing an RDF graph using any (normative or
>      nonnormative) RDF syntax.
> 
> The problem with this is that it forbids use of rdf:text in interchange
> in the future.  In fact, RIF can be used to interchange RDF Graphs (by
> stating ground frame facts,), but it's forbidden by this text from
> including internationalized strings!  More seriously, I expect new
> machine formats for RDF would use rdf:text, but this forbids it.
> 
> I think this can be fixed by adding a little phrase, which I've put in
> all-caps below, just to show the change:
> 
>      Despite the semantic equivalence between typed rdf:text RDF
>      literals and plain RDF literals, the presence of typed rdf:text RDF
>      literals in an RDF graph might cause interoperability problems
>      between RDF tools, as not all RDF tools will support
>      rdf:text. Therefore, before exchanging an RDF graph with other RDF
>      tools, an RDF tool that suports rdf:text MUST replace in the graph
>      each typed rdf:text RDF literal with the corresponding plain RDF
> ->   literal, UNLESS THE EXCHANGE FORMAT BEING USED MANDATES THAT
> ->   RECIEVERS SUPPORT RDF:TEXT.  The notion of graph exchange includes,
>      but is not limited to, the process of serializing an RDF graph
>      using any (normative or nonnormative) RDF syntax.
> 
> The paragraph could be re-written to be smoother, but I think that's the
> minimal change we need here.
> 
>     -- Sandro
> 
>

Received on Monday, 6 April 2009 18:07:00 UTC