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Re: Namespace persistence etc

From: Scott Simmons <ssimmons@opengeospatial.org>
Date: Wed, 13 Jul 2016 06:51:39 -0600
Cc: SDW WG Public List <public-sdw-wg@w3.org>
Message-Id: <BFA93008-7D89-414C-99A5-C25F10E87F9C@opengeospatial.org>
To: Phil Archer <phila@w3.org>
Phil,

No variance from an OGC perspective other than this is better articulated than perhaps we have done!

Best Regards,
Scott

> On Jul 12, 2016, at 11:12 PM, Phil Archer <phila@w3.org> wrote:
> 
> @Scott - please chime in with any variance to this from an OGC perspective.
> 
> Dear all,
> 
> I must begin by apologising for not being on the SSN call today/last night. I could make up some convoluted reason but the truth is that I forgot.
> 
> I know one of the topics discussed was the issue around vocabulary term persistence so I should set out a few things about that.
> 
> The principle is, I think, straightforward: any change made to a vocabulary shouldn't break existing implementations. Since we don't know who has an implementation, we can't write to everyone and ask "if we change this will your thing break?" Therefore we have to be cautious.
> 
> That's what leads to W3C saying that vocabulary terms may not be deleted or their semantics changed radically. But it only applies at the namespace level. If you have a new namespace, you can do what you like since nothing will break. *However* it's going to be really confusing if some terms in the old and new namespaces are the same but with radically different semantics. So my interpretation is:
> 
> Same namespace:
> ===============
> No deletions.
> No changing or tightening or semantics (i.e. don't add a new domain or range - make a sub class|property and put the new restrictions on that)
> Deprecation is OK.
> Loosening semantics is OK (so you *can* remove a domain or range restriction since it is extremely unlikely that doing so will break anyone's existing implementation).
> Adding new terms is fine.
> Clarifying existing definitions is OK.
> Adding new translations of labels is expressly encouraged.
> 
> Different namespace
> ===================
> We can be a little more relaxed here. Recall that documents on w3.org are persistent so the original documentation will always be there (at the original URI or redirected from it).
> 
> No need to replicate the whole of the old vocabulary, so no need to include deprecated terms - they are deprecated by not being included in the new namespace.
> 
> Assuming the vocabulary has the same name then terms that appear in both old and new should broadly be the same although semantics can change a little. It's a matter of judgement.
> 
> The case I keep in mind is Dublin Core/DC Terms. dc:creator took either text or a URI as a value - which was confusing. dcterms:creator should take a URI.
> 
> Hope this helps clarify things.
> 
> Phil.
> 
> -- 
> 
> 
> Phil Archer
> W3C Data Activity Lead
> http://www.w3.org/2013/data/
> 
> http://philarcher.org
> +44 (0)7887 767755
> @philarcher1
> 
Received on Wednesday, 13 July 2016 12:52:05 UTC

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