OK, now I have to submit my other notion after all, which I think addresses some of Steve's concerns. But let me semi-agree with his first paragraph -- I'm enthusiastic, but I think there are a lot of details to be agreed on. I'll come back to that in a separate post.
I had thought it was important to provide a way to enter proposed CF terms in a common way/place, so that they can (a) be used by the originators and the community in the meantime, (b) be seen by the CF folks, and (c) be dispositioned appropriately when CF either accepts them or rejects them. So my proposal was to create a vocabulary, or more precisely an RDF store, that lets us:
1) declare a name that may be proposed as a CF candidate
2) make a statement that the name has been (or even 'is being') submitted to CF for consideration
3a) make a statement that the name has been accepted as a CF name, and therefore is deprecated as a proposed name
3b) make a statement that the name has been rejected as a CF name, and therefore is deprecated as a proposed name
In either 3a or 3b,
4) make a statement that the replacement representation of the name is xyz in some other vocabulary
The relationship of this proposal to the previous thread is that it provides an implementation mechanism for the life cycle of the provisional terms. It also helps assure some of the things Steve is trying to ensure -- some of which only recently became possible with CF, and even that manually, not through any automatable utility, interface, or URI convention.
Anyway, I don't want to encourage a detailed discussion of the above proposal, as it is secondary to Martin's original suggestion, and I feel sure it will have to be considered at some length in TRAC if we get that far. Just wanted to mention that the semantic technologies can enable some very useful views/approaches to some of these problems.
John
On May 12, 2010, at 11:22, Steve Hankin wrote:
> Hi Martin,
>
> You've had two enthusiastic "yes" responses, so I guess I have the privilege to be the wet blanket. So it goes. I will give only a very cautious and limited "yes". Not an outright "no" ... but a suggestion for more thought and discussion.
>
> The proposal here is effectively the creation of 'private tables' as a means of achieving extensibility. We've had an opportunity to see the hazards embedded in this approach as a long-term evolutionary process in WMO. Over time the "custom" tables evolve to have an quasi-official status -- entire sub-communities rely upon them -- but without necessarily a corresponding methodical control over their creation and distribution. With BUFR and GRIB files the proliferation of distinct tables has lead to serious interoperability problems.
>
> To avoid repeating these problems with your proposal, CF clients must be provided with iron-clad ways to be assured that they are referring to the same vocabulary tables that the data author was referring to at the time that the data were written. Since we want CF files to ensure interoperability when there are years separating the writing of data from reading it, your strategy needs to ensure careful version control over the private tables. This imposes a significant burden on you as the creator of a "<project>_standard_name" table -- essentially a requirement to retain and serve out older table versions "in perpetuity" (we could argue over what that means). The use of semantic web technologies will not alter these considerations for the foreseeable future (tho over the long term sophisticated inference engines might ...). The ontologies still need to be informed by correct information, which implies knowledge of the version-controlled private vocabularies.
>
> A "<project>_standard_name" may have one of three life histories: it may never become accepted into the standard_name table; it may be accepted as-is; or it may be accepted with alterations. The following suggested restriction illustrates some of the difficulties: "A variable can contain either a standard_name or <project>_standard_name attribute but not both." What's behind this restriction? Given the uncertain life history of a <project>_standard_name, if it has been in use for (say) a year and is found in thousands of files that are being shared around the community, doesn't that generate a need to continue support for it.
>
> Two alternative approaches (both flawed, of course ... the nature of the beast):
> Should the CF standard_name process, itself, include a "provisional fast-track", that allows names to be added very quickly with no guarantee that they will have a lasting status, but with an iron-clad guarantee that the provisional names will be retained (and so-identified) in version-stamped (older) CF vocabularies.
> or
> Might you be better off using a *truly private* vocabulary of "<project>_standard_name" strings. I.e. one that has no official status in CF at all? There is no violation to the CF standard through doing this. This approach makes it your private responsibility on behalf of your users to deal with files that are created in the period between proposing a CF standard_name and having it become part of the official table
>
> - Steve
>
> ====================
>
> Schultz, Martin wrote:
>>
>> Dear all,
>>
>> we are currently cleaning all files on our TFHTAP multi-model
>> experiment server to make them fully CF(1.0) conformant. It has been
>> about 3 years since we had drafted the original format description of
>> these experiments and also initiated the standard name discussion for
>> chemical constituents (thanks again to Christiane Textor who did a lot
>> of this initial work). Many standard names which we needed have now been
>> defined (thanks to all who contributed and to Allison for maintaining
>> the list!). Nevertheless, there are a number of model variables left for
>> which no standard name has been agreed upon and where we (or the CF
>> mailing list group) also felt that they are too specialized to deserve a
>> "standard" name. From the perspective of the CF community this may not
>> be an issue, but in the context of interoperability (we now operate a
>> WCS server to share these files) the fact that some variables do have a
>> standard_name attribute and others don't poses considerable challenges.
>> The CF convention states that "either standard_name or long_name" should
>> be present. In our view, the long_name attribute is a poor substitute
>> for the standard_name, because it has no rules attached. We are now
>> planning to substitute "illegal" standard_name attributes by a new
>> "htap-_standard_name" attribute, which shall make clear that these names
>> are derived according to the CF guidelines, but they are not accepted
>> standard_names. Such a concept would enable software tools to easily
>> scan additional standard_name tables and make use of the well-defined
>> semantics that a standard_name provides without having to push
>> additional standard_names through the discussion - in particular if they
>> are no so "standard". I can see the danger that certain groups might
>> think it no longer necessary to go through the tedious but ultimately
>> worthwhile discussion process in this mailing list and the meaning of
>> "standard" names could get diluted. However, in my view the advantage of
>> having the possibility to extend the convention without breaking
>> standard-conformance outweighs this potential disadvantage.
>>
>> Specifically I would thus propose to add an optional attribute to
>> the CF documents such as:
>>
>> <project>_standard_name: use this attribute to define the meaning of
>> variables which have no accepted standard_name defined (yet). The
>> project name should be a single string without blanks or underscore
>> characters. These project-specific standard_names must follow the
>> guidelines for the construction of standard_names, but they will not be
>> evaluated by generic tools which test a data file for CF compliance.
>> Groups who wish to define such project-specific standard names should
>> first consider to submit their proposals to the CF mailing list for
>> inclusion in the CF standard name table. A variable can contain either a
>> standard_name or <project>_standard_name attribute but not both. A
>> long_name attribute is not needed when a <project>_standard_name is
>> given.
>>
>>
>> Best regards,
>>
>> Martin
>>
>>
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--------------
I have my new work email address: jgraybeal at ucsd.edu
--------------
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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