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