[OSGeo-Standards] Was: "file" formats. Is: GeoWeb

Baumann, Peter p.baumann at jacobs-university.de
Thu Jul 11 11:44:58 PDT 2013

- well, a coverage is a collection (set) of features, with some particular constraints (gridding, same feature ("pixel") type). This set and its components reflect phenomena, they are "real", a "resource"
- a tile is an artifact resulting from performance optimization. It is not reflecting anything relevant in reality, so it is not a "resource". And on coverages specifically, tiling for clients will fail miserably.
- REST and http discussion is good on the link / graph level of the Web, but has no advantage for discussing coverage handling and its internals. Wrong paradigm.
- even more so when it comes to service functionality. This is all to high level - let's get concrete: we need paradigms to express subsetting, NDVI computation, climate anomaly detection, etc. 
- <advertisement>With the WCS 2 suite we have a rich, flexible toolkit for describing, querying, analyzing coverages independently from their encoding format, and independent from KVP, SOAP, REST.</advertisement> ...Anything you are missing in WCS? Please let me know, I'm sure there is more that can be done on it.


Dr. Peter Baumann- Professor of Computer Science, Jacobs University Bremen
  mail: p.baumann at jacobs-university.detel: +49-421-200-3178, fax: +49-421-200-493178
- Executive Director, rasdaman GmbH Bremen (HRB 26793)http://www.rasdaman.com,
  mail: baumann at rasdaman.com
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From: Raj Singh [rsingh at opengeospatial.org]
Sent: Thursday, July 11, 2013 8:28 PM
To: Rushforth, Peter
Cc: Baumann, Peter; standards at lists.osgeo.org
Subject: Re: [OSGeo-Standards] Was: "file" formats.  Is: GeoWeb

On Jul 11, at 2:15 PM, "Rushforth, Peter" <Peter.Rushforth at NRCan-RNCan.gc.ca> wrote:

>> I think the
>> biggest problem I have with designing RESTful resources
>> around coverage data is the fact that most coverages
>> represent natural phenomena that vary continuously across the
>> earth's surface (or atmosphere, or sub-surface). This means
>> that the actual cell values are only approximations of what
>> is expected to be observed in nature.
> Can a coverage be tiled?  Can you reproduce a coverage data structure by
> re-assembling tiles?

This is exactly the problem. I think coverage loses meaning when it's tiled. It's like graphing a wavelength equation, then snipping out a part of the graph, then trying to recreate the original equation with only that part of the graph. There will probably be many equations that fit the graph. I suppose you could avoid this problem with coverages by maintaining, e.g., something like a "link=source" to the original coverage in the tile data. But I also don't have the professional background in the sciences that use coverages to know if this would be useful.

>> This is why I have a
>> hard time calling anything a resource other than the full coverage.
> But, a FeatureCollection is also a Feature, right?  A collection
> can have in principle an unlimited number of features.   A representation
> is just that: a representation of the resource.  Not the whole thing, necessarily.
> Not the beginning of it, nor the end of it necessarily.  If one
> can figure out how to provide access to a part of a resource,
> and potentially link to other parts of it e.g. link at rel="next".

No problem with anything you say here. Actually I emphatically agree the only problem is figuring out those pesky link relations!

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