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Re: Coverage subgroup update

From: Peter Baumann <p.baumann@jacobs-university.de>
Date: Wed, 20 Jul 2016 08:04:13 +0200
To: Jon Blower <j.d.blower@reading.ac.uk>, Bill Roberts <bill@swirrl.com>, "public-sdw-wg@w3.org" <public-sdw-wg@w3.org>
CC: Maik Riechert <m.riechert@reading.ac.uk>
Message-ID: <578F145D.9060708@jacobs-university.de>
Hi Jon,

of course I am in no way impeding scientific work on establishing and evaluating
alternative concepts, and I am by no means questioning the merits of your approach.

>From a standards point of view, however, it is essential that one term has one
definition, so redefining "coverage" is detrimental. But you open a door by
suggesting your model might become an additional encoding, based on a
compatibility exercise.

PS: Just to mention this, the OGC coverage model never enforced GML (just
aligned to its conceptual structure and offered GML as one option), and neither
did WCS (cf Core). Starting CIS 1.1, JSON and RDF are supported as well, so an
implementation may well reside in RDF world, or NetCDF world, or any other
encoding/service style world exclusively.

cheers,
Peter


On 07/20/2016 01:45 AM, Jon Blower wrote:
>
> Hi Peter,
>
>  
>
> It depends exactly what you mean by “aligned”. Certainly CovJSON uses the same
> high-level concepts of a domain, range and range descriptor. And it’s possible
> to encode a wide variety of coverages in CovJSON – continuous and categorical,
> regular and irregular, gridded and non-gridded, with some embedded semantic
> information. The specification, playground and cookbook illustrate this,
> although they are all currently unfinished (see https://covjson.org)
> <https://covjson.org%29>. If there appears to be a gap (i.e. important
> information that we can’t encode) then please do report this – all the
> development is being done fully out in the open on GitHub and we welcome all
> comments.
>
>  
>
> However, CovJSON deliberately does not attempt to use GML structures as its
> basis, mainly for reasons of simplicity and minimalism. It aims at an audience
> that is unfamiliar with GML. It tries to be a simple and clear format that can
> encode the relevant information accurately using idiomatic JSON, using a
> minimal set of consistent rules. It happens to share quite a lot in common
> with how NetCDF works, but is certainly not a literal translation of NetCDF
> into JSON either.
>
>  
>
> (One important point is that we don’t currently support the “interleaved
> domain and range” structure for coverages. We can maybe try to address this if
> there is enough user demand.)
>
>  
>
> Personally I don’t see any reason why CovJSON could not one day become an OGC
> standard, alongside the other possible coverage encoding formats. I’m not
> pushing hard for this myself at the moment because I would like to test its
> efficacy seriously in the community first – if it turns out to be successful
> and there is community support then that would be a good time to move for full
> standardisation. At the moment, I don’t think we are talking about a full OGC
> spec, although I’m not quite sure what the official OGC status of the document
> resulting from this working group would be (Bill, can you help?)
>
>  
>
> Cheers,
> Jon
>
>  
>
>  
>
>  
>
>  
>
> *From: *Peter Baumann <p.baumann@jacobs-university.de>
> *Organization: *Jacobs University Bremen
> *Date: *Tuesday, 19 July 2016 21:52
> *To: *Bill Roberts <bill@swirrl.com>, "public-sdw-wg@w3.org"
> <public-sdw-wg@w3.org>
> *Cc: *Maik Riechert <m.riechert@reading.ac.uk>, Jon Blower
> <sgs02jdb@reading.ac.uk>
> *Subject: *Re: Coverage subgroup update
>
>  
>
> hm, is this aligned with the OGC coverage model? If not, why do you think that
> OGC could support something not compatible?
> puzzled,
> Peter
>
> On 07/19/2016 10:42 PM, Bill Roberts wrote:
>
>     Hi all
>
>      
>
>     Sorry for being a bit quiet on this over the last month or so - it was as
>     a result of a combination of holiday and other commitments.
>
>      
>
>     However, some work on the topic has been continuing.  Here is an update
>     for discussion in the SDW plenary call tomorrow.
>
>      
>
>     In particular I had a meeting in Reading on 5 July with Jon Blower and
>     fellow-editor Maik Riechert.
>
>      
>
>     During that we came up with a proposed approach that I would like to put
>     to the group.  The essence of this is that we take the CoverageJSON
>     specification of Maik and Jon and put it forward as a potential W3C/OGC
>     recommendation.  See
>     https://github.com/covjson/specification/blob/master/spec.md for the
>     current status of the CoverageJSON specification.
>
>      
>
>     That spec is still work in progress and we identified a couple of areas
>     where we know we'll want to add to it, notably around a URI convention for
>     identifying an extract of a gridded coverage, including the ability to
>     identify a single point within a coverage. (Some initial discussion of
>     this issue at https://github.com/covjson/specification/issues/66
>     <https://github.com/covjson/specification/issues/66>).
>
>      
>
>     Maik and Jon understandably feel that it is for others to judge whether
>     their work is an appropriate solution to the requirements of the SDW
>     group.  My opinion from our discussions and initial review of our
>     requirements is that it is indeed a good solution and I hope I can be
>     reasonably objective about that.  
>
>      
>
>     My intention is to work through the requirements from the UCR again and
>     systematically test and cross-reference them to parts of the CovJSON spec.
>     I've set up a wiki page for that:
>     https://www.w3.org/2015/spatial/wiki/Cross_reference_of_UCR_to_CovJSON_spec  That
>     should give us a focus for identifying and discussing issues around the
>     details of the spec and provide evidence of the suitability of the
>     approach (or not, as the case may be). 
>
>      
>
>     There has also been substantial interest and work within the coverage
>     sub-group on how to apply the RDF Data Cube vocabulary to coverage data,
>     and some experiments on possible adaptations to it.  The main potential
>     drawback of the RDF Data Cube approach in this context is its verbosity
>     for large coverages.  My feeling is that the standard RDF Data Cube
>     approach could be a good option in the subset of applications where the
>     total data volume is not excessive - creating a qb:Observation and
>     associated triples for each data point in a coverage.  I'd like to see us
>     prepare a note of some sort to explain how that would work.  I also think
>     it would be possible and desirable to document a transformation algorithm
>     or process for converting CoverageJSON (with its 'abbreviated' approach to
>     defining the domain of a coverage) to an RDF Data Cube representation.
>
>      
>
>     So the proposed outputs of the group would then be:
>
>      
>
>     1) the specification of the CoverageJSON format, to become a W3
>     Recommendation (and OGC equivalent)
>
>     2) a Primer document to help people understand how to get started with it.
>      (Noting that Maik has already prepared some learning material at
>     https://covjson.gitbooks.io/cookbook/content/)
>
>     3) contributions to the SDW BP relating to coverage data, to explain how
>     CovJSON would be applied in relevant applications
>
>     4) a note on how RDF Data Cube can be used for coverages and a process for
>     converting CovJSON to RDF Data Cube
>
>      
>
>     Naturally I expect to discuss this proposal in plenary and coverage
>     sub-group calls!
>
>      
>
>     Best regards
>
>      
>
>     Bill
>
>      
>
>      
>
>      
>
>      
>
>      
>
>      
>
>
>
> -- 
> Dr. Peter Baumann
>  - Professor of Computer Science, Jacobs University Bremen
>    www.faculty.jacobs-university.de/pbaumann
> <http://www.faculty.jacobs-university.de/pbaumann>
>    mail: p.baumann@jacobs-university.de <mailto:p.baumann@jacobs-university.de>
>    tel: +49-421-200-3178, fax: +49-421-200-493178
>  - Executive Director, rasdaman GmbH Bremen (HRB 26793)
>    www.rasdaman.com <http://www.rasdaman.com>, mail: baumann@rasdaman.com <mailto:baumann@rasdaman.com>
>    tel: 0800-rasdaman, fax: 0800-rasdafax, mobile: +49-173-5837882
> "Si forte in alienas manus oberraverit hec peregrina epistola incertis ventis dimissa, sed Deo commendata, precamur ut ei reddatur cui soli destinata, nec preripiat quisquam non sibi parata." (mail disclaimer, AD 1083)
>  
>  

-- 
Dr. Peter Baumann
 - Professor of Computer Science, Jacobs University Bremen
   www.faculty.jacobs-university.de/pbaumann
   mail: p.baumann@jacobs-university.de
   tel: +49-421-200-3178, fax: +49-421-200-493178
 - Executive Director, rasdaman GmbH Bremen (HRB 26793)
   www.rasdaman.com, mail: baumann@rasdaman.com
   tel: 0800-rasdaman, fax: 0800-rasdafax, mobile: +49-173-5837882
"Si forte in alienas manus oberraverit hec peregrina epistola incertis ventis dimissa, sed Deo commendata, precamur ut ei reddatur cui soli destinata, nec preripiat quisquam non sibi parata." (mail disclaimer, AD 1083)
Received on Wednesday, 20 July 2016 06:05:22 UTC

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