- From: Jeremy Carroll <jeremy@topquadrant.com>
- Date: Tue, 08 Mar 2011 17:38:15 -0800
- To: Ivan Herman <ivan@w3.org>
- CC: RDF Working Group WG <public-rdf-wg@w3.org>
I realized I should have given a simple answer. The decision was based on not wanting to require an XML subsystem within an RDF reasoner. Therefore the XML processing is confined to the RDF/XML parser that has to handle XML anyway. Jeremy On 3/8/2011 5:27 PM, Jeremy Carroll wrote: > Hi Ivan > http://www.w3.org/TR/2003/WD-rdf-concepts-20031010/#section-substantive-Revisions > > Under "XMLLiteral simplification" gives the blow by blow account. > > There is text embedded in > http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0170.html > > Joe Reagle says: > [[ > > I presume that the reason you even care how the xml-literal is > represented >> > is that you will want to compare RDF instances (which might contain >> > xml-literals) to see if they are identical at some point? > ]] > > The current design is intended to make that easy, and put the burden > of XML processing within the RDF/XML parser. > A turtle or N3 parser is not required to have an XML subsystem, > whereas the older design, which canonicalized as part of the lex2value > mapping required all RDF implementations to be able to do that. > > Notice also point i in > http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0335.html > [[ > > An example fix would be > to require an RDF/XML parser to use a specific canonicalization on > input. > > ]] > A proposal that was accepted in full. > > Jeremy > > > On 3/8/2011 12:41 AM, Ivan Herman wrote: >> Jeremy, >> >> just want to understand... what was the reason xc14n was required on >> the lexical space? I would expect that xc14n is important to be able >> to compare xml literals but that is a value space issue. Just like >> 123.456 is identical, in value space, to 123.4560000 >> >> Thanks >> >> Ivan >> >> On Mar 7, 2011, at 20:28 , Jeremy Carroll wrote: >> >>> The motivation in the 1999 M&S spec, and the 2004 Recs for XML >>> Literals were to do with I18N use cases involving HTML (and in some >>> of them Ruby) >>> >>> I believe that for at least some of these use cases we would now >>> recommend RDFa. >>> >>> I think there are some use cases that are not addressed by RDFa. >>> >>> Once you take the use cases seriously, then you end up somewhere not >>> a million miles away from the current specs, with all their problems. >>> >>> I suspect an underlying error in the 2002-2004 work was the >>> following incorrect reasoning: >>> - it is important for RDF to carry rich text literals (e.g. >>> involving Ruby markup) >>> - it is important to be able to tell if two RDF fragments are the same >>> Hence: >>> - it is important to be able to compare two rich text literals in >>> RDF [It is this that leads to the XC14N dance] >>> >>> Jeremy >>> >>> >>> On 3/7/2011 5:35 AM, Ivan Herman wrote: >>>> On Mar 7, 2011, at 14:25 , RDF Working Group Issue Tracker wrote: >>>> >>>>> RDF-ISSUE-13 (RDF XMLLiterals): Review RDF XML Literals [Cleanup >>>>> tasks] >>>>> >>>>> http://www.w3.org/2011/rdf-wg/track/issues/13 >>>>> >>>>> Raised by: Andy Seaborne >>>>> On product: Cleanup tasks >>>>> >>>>> RDF Concepts: >>>>> http://www.w3.org/TR/rdf-concepts/#section-XMLLiteral >>>>> >>>>> RDF Syntax: >>>>> http://www.w3.org/TR/REC-rdf-syntax/#section-Syntax-XML-literals >>>>> >>>>> The lexical space of RDF XML Literals is XML fragments which are >>>>> required to be "exclusive canonical XML". The lexical space and >>>>> the value space are in 1-1 correspondence. The rules are quite >>>>> complicated. These rules for canonicalization apply to the lexical >>>>> form; equality testing can be done using string compare. >>>>> >>>>> Canonicalization rules include no use of<tag/> and that >>>>> attributes must be in sorted order (this is not an exhaustive list). >>>>> >>>>> A consequence of this is that many correct XML fragments are not >>>>> legal as XML Literals because they do not correspond to exclusive >>>>> canonicalization. >>>>> >>>>> Possible cleanup includes partially relaxing the lexical space >>>>> restrictions while retaining the value space so that fragments can >>>>> be used as XML literals without complex processing. >>>>> >>>> +10^infinite >>>> >>>> I know of no RDF serializers around that would produce correct XML >>>> Literals in this sense. They all produce valid XML, with hopefully >>>> the right namespace declarations (though that does not always >>>> happen either) but they certainly do not necessarily go through the >>>> extra mile of canonicalization. And there is no reason for that >>>> either: canonicalization comes into place when two XML fragments >>>> must be compared as strings; but this should be done in value space >>>> and not in lexical space... >>>> >>>> Ivan >>>> >>>>> RDF XML Literals are the only datatype hard wired into RDF. >>>>> >>>>> If a Turtle document is to be validated, will that require access >>>>> to an XML parser and canonicalization engine? >>>>> >>>>> >>>>> >>>>> >>>> ---- >>>> 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 >>>> >>>> >>>> >>>> >>>> >> >> ---- >> 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 >> >> >> >> >> >
Received on Wednesday, 9 March 2011 01:38:38 UTC