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Re: DC vs. DCTERMS in initial context

From: Gregg Kellogg <gregg@greggkellogg.net>
Date: Fri, 31 Aug 2012 09:55:58 -0400
To: Oskar Welzl <lists@welzl.info>
CC: Ivan Herman <ivan@w3.org>, W3C RDFa Community <public-rdfa@w3.org>, Thomas Baker <tom@tombaker.org>
Message-ID: <250B64BB-6AE2-48C4-91DD-4C98EA09792A@kellogg-assoc.com>
On Aug 31, 2012, at 4:09 AM, "Oskar Welzl" <lists@welzl.info> wrote:

> 
>> As far as I remember, the advice of DCMI (Tom, correct me if I am
>> wrong) was to use only /dc/terms in future, [...]
>> Personally, I would like to defer the choice to DCMI.
> 
> The choice to prefer DCTerms for current/future use is one thing.
> 
> The problem arises when you change existing RDFa to RDFa 1.1 and rely on
> the initial context. In this case, the RDF output doesn't comply to the
> DCMI recommendations. I came across this when I tried to convert the
> RDFa 1.0 example in wikipedia [1] to RDFa 1.1, removing XML namespace
> declarations while doing so.
> 
> I expected the same RDF triples thanks to the initial context, but got 
> 
> <http://example.org/john-d/> 
>    <http://purl.org/dc/terms/creator> "Jonathan Doe"@en;
> 
> instead of the original
> <http://example.org/john-d/> 
>    <http://purl.org/dc/elements/1.1/creator> "Jonathan Doe"@en;
> 
> Now dc:creator (or http://purl.org/dc/elements/1.1/creator) may be used
> with literals, so the original RDFa 1.0 was OK.
> OTOH, dcterms:creator, according to the user guide [2], must not be used
> with literals. I had overrule the initial context and insert the
> corresponding prefix into the HTML+RDFa 1.1 example to make it work.
> 
> I don't know how many will change from existing markup to 1.1, but if
> they do there'll be some more unwanted literals as dcterms:creators out
> there. 
> 
> Maybe it'd be enough to point this out somewhere. I have no idea how
> relevant it will become.

One purpose of the initial context is as a fallback mechanism, in case a document is authored accidentally without appropriate prefix definitions. For example, this made many documents using OGP valid RDFa again.

We had considered that a best practice would be for authors to not rely on prefixes defined in the initial context and recommend that authors define their own @prefix definitions. The initial context is a convenience method which doesn't replace the need for authors with specific vocabulary needs from being explicit. As new use of DCMI should use dc/terms anyway, providing a convenience mechanism makes sense, IMO.

Gregg

> Cheers
> Oskar
> 
> [1] http://en.wikipedia.org/wiki/RDFa#XHTML.2BRDFa_1.0_example
> [2]
> http://wiki.dublincore.org/index.php/User_Guide/Publishing_Metadata#dcterms:creator
> 
> 
>> Cheer
>> 
>> Ivan
>> 
>> On Aug 29, 2012, at 20:42 , Oskar Welzl wrote:
>> 
>>> I only noticed a few day ago that both dc: and dcterms: are used for 
>>> http://purl.org/dc/terms/
>>> in the initial context. In most examples or practical uses so far, I've
>>> seen dc: being used for 
>>> http://purl.org/dc/elements/1.1/
>>> instead, making it easy to distinguish between the legacy vocabulary and
>>> DCTerms. (Practical example:
>>> http://wiki.dublincore.org/index.php/User_Guide/Publishing_Metadata)
>>> 
>>> 
>>> What's the rationale behind this decision in the initial context? 
>>> 
>>> Oskar
>>> 
>>> 
>> 
>> 
>> ----
>> Ivan Herman, W3C Semantic Web Activity Lead
>> Home: http://www.w3.org/People/Ivan/
>> mobile: +31-641044153
>> FOAF: http://www.ivan-herman.net/foaf.rdf
>> 
>> 
>> 
>> 
>> 
> 
> 
> 
Received on Friday, 31 August 2012 13:56:43 UTC

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