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Re: Coverage subgroup update

From: George Percivall <gpercivall@opengeospatial.org>
Date: Wed, 20 Jul 2016 08:04:39 -0400
Cc: "public-sdw-wg@w3.org" <public-sdw-wg@w3.org>, Bill Roberts <bill@swirrl.com>
Message-Id: <71A44A9A-9B7B-4C51-8545-EB53A94374FD@opengeospatial.org>
To: Jon Blower <j.d.blower@reading.ac.uk>, Peter Baumann <p.baumann@jacobs-university.de>, Maik Riechert <m.riechert@reading.ac.uk>
This is a relevant part of this discussion:
https://covjson.org/spec/#differences-to-ogc-coverage-implementation-schema-cis <https://covjson.org/spec/#differences-to-ogc-coverage-implementation-schema-cis>



> On Jul 20, 2016, at 2:30 AM, Jon Blower <j.d.blower@reading.ac.uk> wrote:
> 
> Hi Peter,
>  
> Ø  redefining "coverage" is detrimental.
>  
> To my knowledge we are not redefining “coverage”. The term is defined in ISO19123 (which gives the overall abstract concepts as you know) and I consider CovJSON to be fully conceptually compatible with that. As has been discussed many times, there are many ways to concretely serialise a coverage, all of which may be compatible with the abstract concepts of ISO19123.
>  
> If you can point to a specific instance where you believe we are not compatible with the abstract model, please do point it out and we will look at it seriously.
>  
> Ø  your model might become an additional encoding, based on a compatibility exercise.
>  
> Yes, exactly. I imagine there would be some kind of a mapping exercise, a bit like the mapping to the existing CF-NetCDF standard.
>  
> Cheers,
> Jon
>  
> From: Peter Baumann <p.baumann@jacobs-university.de <mailto:p.baumann@jacobs-university.de>>
> Organization: Jacobs University Bremen
> Date: Wednesday, 20 July 2016 07:04
> To: Jon Blower <sgs02jdb@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>
> Subject: Re: Coverage subgroup update
>  
> 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> <mailto:p.baumann@jacobs-university.de>
>> Organization: Jacobs University Bremen
>> Date: Tuesday, 19 July 2016 21:52
>> To: Bill Roberts <bill@swirrl.com> <mailto:bill@swirrl.com>, "public-sdw-wg@w3.org" <mailto:public-sdw-wg@w3.org> <public-sdw-wg@w3.org> <mailto:public-sdw-wg@w3.org>
>> Cc: Maik Riechert <m.riechert@reading.ac.uk> <mailto:m.riechert@reading.ac.uk>, Jon Blower <sgs02jdb@reading.ac.uk> <mailto: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.  Seehttps://github.com/covjson/specification/blob/master/spec.md <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 <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/ <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 <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)
>  
>  


Received on Wednesday, 20 July 2016 12:05:31 UTC

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