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Re: [RIF][Admin] Minutes Telecon 26 August 2008

From: Dave Reynolds <der@hplb.hpl.hp.com>
Date: Wed, 27 Aug 2008 15:37:47 +0100
Message-ID: <48B566BB.2070202@hplb.hpl.hp.com>
To: Jos de Bruijn <debruijn@inf.unibz.it>
CC: public-rif-wg@w3.org

Jos de Bruijn wrote:
> <snip/>
> 
>> <DaveReynolds> Stella - the "mathematical english" is normative, the
>> presentation syntax and it's EBNF is non-normative, the semantics
>> actually refers to the mathematical English - at least that's how I
>> understand it.
> 
> The mathematical English is the specification of the presentation
> syntax. The BNF is only for illustrative purposes.

Yes, that was clarified further down the chat. My error.

>> Axel: Predicate that takes rdf:text and language range, matching eg all
>> "en" tags.
> 
> Why would you want a predicate for that? You can extract the language
> tag and check equality. See also [1]
> 
> [1] http://lists.w3.org/Archives/Public/public-rif-wg/2008Aug/0104.html

Because lang tag matching is not the same as lang tag equality, that's 
why it takes 19 pages to specify the match algorithm in the RFC 
(RFC4647) :-) Just for illustration here's an example from the RFC:

""" the extended language range "de-*-DE"
    (or its synonym "de-DE") matches all of the following tags:
       de-DE (German, as used in Germany)
       de-de (German, as used in Germany)
       de-Latn-DE (Latin script)
       de-Latf-DE (Fraktur variant of Latin script)
       de-DE-x-goethe (private-use subtag)
       de-Latn-DE-1996 (orthography of 1996)
       de-Deva-DE (Devanagari script)
    The same range does not match any of the following tags for the
    reasons shown:
       de (missing 'DE')
       de-x-DE (singleton 'x' occurs before 'DE')
       de-Deva ('Deva' not equal to 'DE')
"""

>> Dave: Fine. Alg the same, just args different.
>> ... Can lang tag be empty xs:string?
> 
> Shouldn't the language tag be a string specified by a specific RFC or
> its successor?

As I understand it that is the proposal except for the allowance of 
empty lang tags.

>> Dave: Normally no need for testing non-emptiness.
> 
> You can test string-length=0

Of course, I wasn't suggesting it is hard to test for empty strings but 
was surprised at the need to do so. It's like returning null in Java 
instead of throwing an exception - you end up with lots of extra guards 
in your code. I had previous thought that:

    pred:isText(?x) & ?l = func:lang(?x)

would result in ?l being a real language tag and so would not need an 
additional guard. That's not the case, but I'm over my surprise now.

Dave
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Received on Wednesday, 27 August 2008 14:39:30 GMT

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