[CF-metadata] Web reference to a standard name?

Lowry, Roy K. rkl at bodc.ac.uk
Fri Dec 17 09:37:25 MST 2010


Hi Richard,

This echoes a discussion in BODC this afternoon and a thought I had some while ago in that having terms inherit the version number of the list in which they reside was not the best of ideas. However, we concluded that maintenance of list versions was a good idea, particularly if the list governance permits deprecation.

I'm not aware of anybody maintaining version numbers at the term level for the Standard Names. Establishing them retrospectively wouldn't be a pleasant task and I don't think there's anything to be gained from their introduction from this point onwards. 

Cheers, Roy.

-----Original Message-----
From: cf-metadata-bounces at cgd.ucar.edu [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Hattersley, Richard
Sent: 17 December 2010 16:13
To: John Graybeal; Jeff deLaBeaujardiere
Cc: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] Web reference to a standard name?

It would seem that the two conflicting requirements, which I'll
caricature as "rigorous version control" and "pragmatic usability",
could go some way to being reconciled by using term-specific version
numbers.

Instead of:
	<some_prefix>/<cf_vocab_number>/<term> (e.g.
.../P071/16/CFSN0023)
Or:
	<some_prefix>/<term> (e.g. .../parameter/air_temperature)

You have:
	<some_prefix>/<term>/<term_version>

Where the term_version is only updated when the definition of the term
changes - not when a release of the standard name table occurs. Thus
avoiding the proliferation of identifiers.

This would still leave a discussion on what constitutes a "change", as
it's quite possible one may wish to allow minor edits (eg. spelling
corrections) for pragmatic reasons.


Richard Hattersley  AVD  Expert Software Developer
Met Office  FitzRoy Road  Exeter  Devon  EX1 3PB  United Kingdom
Tel: +44 (0)1392 885702  Fax: +44 (0)1392 885681
Email: richard.hattersley at metoffice.gov.uk  Website:
www.metoffice.gov.uk


-----Original Message-----
From: cf-metadata-bounces at cgd.ucar.edu
[mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of John Graybeal
Sent: 17 December 2010 00:16
To: Jeff deLaBeaujardiere
Cc: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] Web reference to a standard name?

I offer my two cents on versioned terms, prompted by the 'absolutely
right' phrasing :->.  I am firmly straddling the fence on this question.

There are multiple science users and many technical opinions that say
not having versions is absolutely wrong.  The circumstances that could
make 'current' *not* what you want include:
- you need to understand what definition (or other statements) was in
effect when the tag was applied
- you want to understand the transitions that the definition (or other
statements) has undergone over time
- the meaning of a term actually is significantly different than it used
to be
- additional meanings are associated with a term (e.g., an acronym is
repurposed by another organization) at a later date

I believe the last happens much more often than your confidence suggest
-- perhaps especially in emerging fields or those that are newly
developing documented vocabularies, extremely advanced or subjective
fields, and concepts that get 'culturally adopted', e.g., turned into a
pejorative (slang (that last not our problem, for the most part).  I
don't see how the exclusive use of non-versioned terms supports these
situations.

So while I appreciate the motivations for not including versions, I
think versions have to be offered by the system, and ideally should be
used where unique persistent identifiers are required. 

John


On Dec 16, 2010, at 13:08, Jeff deLaBeaujardiere wrote:

> Actually, my recollection is that EPSG & OGC proposed to include
version numbers, and several of us argued against it and managed to
convince them.  I would have to dig up old emails to find out for
certain who was in which camp, however.
> 
> Regards,
> Jeff DLB
> 
> On 2010-12-16 15:57, Lowry, Roy K. wrote:
>> Hi Jeff,
>> 
>> It's interesting to see the difference of opinion between the
standards developers (the idea of version number in URI came from the
OGC URN specification: interesting how EPSG came to a different
conclusion) and those who have to live with the consequences. The more I
think about it, the more I think you and Benno are absolutely right.
>> 
>> Cheers, Roy.
>> ________________________________________
>> From: cf-metadata-bounces at cgd.ucar.edu 
>> [cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Jeff deLaBeaujardiere

>> [Jeff.deLaBeaujardiere at noaa.gov]
>> Sent: 16 December 2010 19:40
>> To: John Graybeal
>> Cc: cf-metadata at cgd.ucar.edu
>> Subject: Re: [CF-metadata] Web reference to a standard name?
>> 
>> On 2010-12-14 12:56, John Graybeal wrote:
>>> Just to be crystal clear, the places where you have '16' could also
have 'current' (if I understand correctly what Roy was saying about
their server), and the mmisw one could also be served with a particular
version ID (analogous to the NERC example).
>> 
>> I think it is of the utmost importance to have a URI that does not 
>> include a version number and always provides the latest answer. 
>> Otherwise you have a proliferation of identifiers mean the same thing

>> but appear to change every time the overall vocabulary is updated.
You can also have a version-specific entry if desired.
>> 
>> There were similar discussions regarding identifiers for coordinate 
>> reference system identifiers from EPSG (European Petroleum Survey 
>> Group), and it was fortunately recognized that a version-less URI was
essential.
>> 
>> -Jeff
>> 
>> 
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John Graybeal   <mailto:jgraybeal at ucsd.edu> 
phone: 858-534-2162
System Development Manager
Ocean Observatories Initiative Cyberinfrastructure Project:
http://ci.oceanobservatories.org
Marine Metadata Interoperability Project: http://marinemetadata.org   

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