Re: RDF WG Resolution Regarding Various Forms of String Literals

* Ivan Herman <ivan@w3.org> [2011-06-16 15:19+0200]
> I do not see from this formalism where language tags are handled, however.

I've highlighted the language tag generation below.

> Those are _not_ covered by the WG resolution...

The RDF WG intends to remove simple literals (plain literals with no language tag) from the model, declaring them all to be xsd:string (though still preferably written "ab"). The DM maps from an AST representing SQL RDBs to an AST representing the RDF model. Since we define the DG in terms of the RDF model, it would be polite of us to use the same model.

> Ivan
> 
> On Jun 16, 2011, at 14:41 , Eric Prud'hommeaux wrote:
> 
> > * Ivan Herman <ivan@w3.org> [2011-06-16 09:36+0200]
> >> I am not sure this has an effect on R2RML or DM; possibly not. But you may want to know about that anyway!
> > 
> > It could simplify
> > [[
> > [46] ⟦r, c⟧lex = let p = ⟦table(r), fk⟧col in
> >                 let v = value(r, c) in
> >                 let d = datatype(header(table(r))(c)) in
> >                 if v is NULL then ∅
> >                 else if d is String then {(p, v)}

There is a special case here mapping database terms in the String domain to a simple literal v. We would no longer need the "if d is String then...else" exception.

> >                      else let datatype_iri = ⟦d⟧datatype in
> >                           {(p, (v, datatype_iri))}
> > ]] — http://www.w3.org/2001/sw/rdb2rdf/directMapping/#lexical-semantics
> > and add a line to
> > [[
> > [50] ⟦d⟧datatype = if d is Int then XSD:integer
> >                   else if d is Float then XSD:float
> >                   else if d is Date then XSD:date

This will need an extra mapping from SQL String to xsd:string. This is, conveniently, concordant with the draft ISO SQL spec's mapping of SQL types to XSD types.

> >                   ⋯
> > ]] — http://www.w3.org/2001/sw/rdb2rdf/directMapping/#datatype-semantics
> > . I think we should explicitly call out that the datatype mapping is now more uniform (get's rid of "if d is String then {(p, v)}") and mention parenthetically to the reader that "ab"^^xsd:string is actually written "ab".
> > 
> >> Ivan
> >> 
> >> Begin forwarded message:
> >> 
> >>> Resent-From: public-rdf-wg@w3.org
> >>> From: David Wood <david@3roundstones.com>
> >>> Date: June 15, 2011 18:39:19 GMT+02:00
> >>> To: Manu Sporny <msporny@digitalbazaar.com>, Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>, Lee Feigenbaum <lee@thefigtrees.net>
> >>> Cc: RDF Working Group WG <public-rdf-wg@w3.org>, W3C SW CG Group <w3c-semweb-cg@w3.org>, public-rdf-dawg@w3.org
> >>> Subject: RDF WG Resolution Regarding Various Forms of String Literals
> >>> message-id: <5F656216-FE45-426E-A93E-4E90DDC3BE3D@3roundstones.com>
> >>> 
> >>> Hi all,
> >>> 
> >>> The RDF working group resolved our ISSUE-12 [1] today, which is intended to "reconcile various forms of string literals".
> >>> 
> >>> We resolved to accept the proposal at:
> >>> http://www.w3.org/2011/rdf-wg/wiki/StringLiterals/AbolishUntaggedPlain
> >>> with the modification that preferred output form (SHOULD) is "foo" not "foo"^^xsd:string in RDF; and we recommend that SPARQL and other WGs do the same.
> >>> 
> >>> Discussion highlighted several possible areas of concern, which we believe the current proposal addresses.  Specifically, it was noted that:
> >>> 
> >>> - The forms "foo" and "foo"^^xsd:string are equivalent input syntaxes.
> >>> - The form "foo" is the preferred output syntax.
> >>> - The WG suggests retaining the term "plain literal" in documents to avoid unnecessary rework.  Such plain literals would be considered semantically equivalent to xsd:strings.
> >>> 
> >>> NB: This resolution makes *no statement* about language-tagged literals (e.g. "foo"@en).
> >>> 
> >>> We invite discussion regarding the ramifications of this resolution to other working groups and implementors.
> >>> 
> >>> Regards,
> >>> Dave
> >>> 
> >>> [1] http://www.w3.org/2011/rdf-wg/track/issues/12
> >>> 
> >>> 
> >>> 
> >> 
> >> 
> >> ----
> >> Ivan Herman, W3C Semantic Web Activity Lead
> >> Home: http://www.w3.org/People/Ivan/
> >> mobile: +31-641044153
> >> PGP Key: http://www.ivan-herman.net/pgpkey.html
> >> FOAF: http://www.ivan-herman.net/foaf.rdf
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> > 
> > -- 
> > -ericP
> > 
> 
> 
> ----
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
> mobile: +31-641044153
> PGP Key: http://www.ivan-herman.net/pgpkey.html
> FOAF: http://www.ivan-herman.net/foaf.rdf
> 
> 
> 
> 
> 

-- 
-ericP

Received on Thursday, 16 June 2011 14:05:38 UTC