RE: A summary of the proposal for resolving the issues with rdf:text --> Could you please check it one more time?



> -----Original Message-----
> From: Boris Motik [mailto:boris.motik@comlab.ox.ac.uk]
> Sent: 20 May 2009 15:58
> To: 'Eric Prud'hommeaux'
> Cc: Seaborne, Andy; 'Alan Ruttenberg'; public-rdf-text@w3.org; 'Sandro
> Hawke'; 'Axel Polleres'
> Subject: RE: A summary of the proposal for resolving the issues with
> rdf:text --> Could you please check it one more time?
> 
> Hello,
> 
> I have to agree that the text in the rdf:text specification might not
> reflect
> correctly the intentions I expressed. Quite frankly, we (i.e., the
> authors of
> the rdf:text specification) haven't been really aware of all the
> repercussions
> and possible interpretations of our spec. The text you refer to at the
> end of
> this e-mail has been introduced as a reaction to one of the earlier
> comments by
> the SPARQL WG.
> 
> Nevertheless, here is what the goals of rdf:text are:
> 
> 1. Both RIF and OWL 2 find the distinction between plain and typed
> literals
> painful. This is because, whenever one refers to literals, one needs two
> subcases: for a plain and for a typed literal. Both RIF and OWL 2 have
> independently come up with exactly the same idea: they opted to
> represent the
> "semantic content" of plain literals through typed literals whose value
> is the
> same as the corresponding plain literals. This makes the definitions and
> the
> semantic treatment of literals in both RIF and OWL 2 much simpler.
> 
> 
> 2. Both RIF and OWL 2 need a mechanism to refer to the set of all plain
> literals. For example, in OWL 2 you might want to say "the range is a
> piece of
> text". In OWL 2 this is very important because of facets. Using a
> datatype for
> this purpose is natural. Both RIF and OWL 2 have chosen to follow the
> definitions of datatypes from XML Schema. Thus, each datatype consists
> of a set
> of lexical values, a value space, and a L2V mapping. Plain literals do
> not
> follow these principles; therefore, rdf:text defines lexical values that
> encode
> the content of plain literals.
> 
> 
> Now as I have already said, we have not had the complete store as clear
> in our
> minds right from the beginning. Given all the LC comments (which have by
> the way
> have been quite useful and have significantly improved the spec),
> however, both
> RIF and OWL 2 have agreed that the view I proposed in my e-mail is the
> appropriate one (at least from the RIF and OWL 2 points of view). As
> I've stated
> in my summary e-mail, to achieve this we simply need to remove from the
> specification any special treatment of rdf:text: this should be a
> datatype like
> any other. This is precisely the part of the document that you are
> referring to.
> 
> Thus, the final version of the document would not mention any
> interoperability
> problems. Furthermore, we may also rework the introduction to make the
> intention
> behind rdf:text clearer.
> 
> Regards,
> 
>  Boris

Recap:

Another goal is data-exchange, between systems that have different capabilities, including different entailment choices.  Introducing alternative representations of the same thing is not good.  We all have to live with standards because the cost of changes is so high so we work within them where possible.  Standards are a compromise.

This can be met by:

When reading RDF data, systems are free and correct to convert "foo"@en to an rdf:text form.
  This is just stating they are semantically equivalent.
 
When exposing in an RDF form, use the "foo"@en form.
  This includes graph exchange and SPARQL.

This leaves the 2 goals above untouched.  It maximising interoperation with existing systems.
 
 Andy

Received on Thursday, 21 May 2009 09:35:34 UTC