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Re: Regarding the SHOULD for NFC in RDF Literals

From: Richard Cyganiak <richard@cyganiak.de>
Date: Mon, 23 Sep 2013 11:32:44 +0100
Cc: public-rdf-comments@w3.org
Message-Id: <DBFFDCF5-6681-48DE-9C43-415493F7A3ED@cyganiak.de>
To: Sebastian Hellmann <hellmann@informatik.uni-leipzig.de>
(Not an official WG response, but personal opinion)

The short answer is backwards compatibility with legacy content. It said SHOULD in the 2004 version of RDF. If we now change SHOULD to MUST, then some existing RDF 2004 documents would be invalid RDF 1.1 documents. The RDF WG's charter strongly discourages breaking backwards compatibility. I'd say that's sufficient justification for leaving the SHOULD in place.

That being said, as far as I recall, the WG has not seen any evidence that such existing legacy content actually exists, nor has it seen any evidence that changing SHOULD to MUST would in practice increase compatibility. In the absence of evidence pointing in either direction, retaining backwards compatibility seems like a safe and defensible choice.


On 22 Sep 2013, at 21:42, Sebastian Hellmann wrote:

> Hello all,
> I was asking myself another question regarding the "should" in 3.3. http://www.w3.org/TR/rdf11-concepts/#section-Graph-Literal
>> 	 a lexical form, being a Unicode [UNICODE] string, which SHOULD be in Normal Form C [NFC],
> http://www.ietf.org/rfc/rfc2119.txt says regarding SHOULD: 
>> 3. SHOULD   This word, or the adjective "RECOMMENDED", mean that there
>>    may exist valid reasons in particular circumstances to ignore a
>>    particular item, but the full implications must be understood and
>>    carefully weighed before choosing a different course.
> I am not sure, what reasons could exist not to require NFC . N-Triples doesn't seem to use ASCII any more in its next version. What is the hold up to change this to a MUST and write a validation test case? 
> I am just asking out of curiosity. The topic is complex and the "full implications must be understood and carefully weighed before choosing a different course" justify a SHOULD as well. 
> All the best,
> Sebastian
> -- 
> Dipl. Inf. Sebastian Hellmann
> Department of Computer Science, University of Leipzig 
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Received on Monday, 23 September 2013 10:33:12 UTC

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