Re: What do the resolutions on language tags mean for equality of tagged strings?

I’m referring to the current Editor’s Draft [1], not the current Working Draft.  See section 3.3 of the current Editor’s Draft, in particular the changed definition of “language tag” and “literal equality” (now called “literal term equality”, which is why I used “term equality” and “value equality”).  One of the changes “[i]mplemented [a resolution] regarding rdf:langString case sensitivity” [2].

[1]: https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#
[2]: https://dvcs.w3.org/hg/rdf/file/0d21aa9127d0/rdf-concepts/index.html


From: Gregg Kellogg 
Sent: Sunday, June 09, 2013 6:08 PM
To: Peter Occil 
Cc: public-rdf-comments@w3.org 
Subject: Re: What do the resolutions on language tags mean for equality of tagged strings?

On Jun 9, 2013, at 7:03 AM, Peter Occil <poccil14@gmail.com> wrote:


  I see that most of the issues involving language tags have been resolved. I need clarification though about term-equality and "value equality" of language-tagged strings.

  First, literal term equality: Are the following literals considered term-equal?

      "chat"@FR
      "chat"@fr
      
  I don't think so, since the language tags have different case. I do believe, though, that those two literals have the same value, since both have the string value "chat" and the lower-cased language tag "fr" (only lower-case language tags are in the value space). Am I right?

RDF Concepts says that [[[two terms are equal if and only if the two lexical forms, the two datatype IRIs, and the two language tags (if any) compare equal character by character]]] [1]. It also says that language tags MUST be normalized to lowercase. I believe this means that the two literals are, in fact, the same term. Furthermore, if a concrete syntax allowed it, I would say that "chat"@fr^^rdf:langString was also the same term, just as "chat" and "chat"^^xsd:string are the same term.

As it happens, I think that my implementation currently keeps the original case of the language; a future update for RDF 1.1 will likely normalize on creation and gain some performance on comparison.


  --Peter

Gregg 

[1] http://www.w3.org/TR/rdf11-concepts/#section-Graph-Literal