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Re: UCR issue: phrasing of CRS requirement(s)

From: Andrea Perego <andrea.perego@jrc.ec.europa.eu>
Date: Wed, 20 May 2015 18:09:08 +0200
Message-id: <CAHzfgWCwBu=Ljhhr4=RRC2sTDFu9pXy6DpR4q0OG+T2zZ24bqg@mail.gmail.com>
To: Krzysztof Janowicz <janowicz@ucsb.edu>
Cc: Simon Cox <Simon.Cox@csiro.au>, Lars Svensson <L.Svensson@dnb.de>, Raphaël Troncy <raphael.troncy@eurecom.fr>, Kerry Taylor <Kerry.Taylor@csiro.au>, Ed Parsons <eparsons@google.com>, SDW WG <public-sdw-wg@w3.org>
Probably I'm mistaken, but I don't think Raphaël and Lars were
necessarily asking for a "full" RDF/OWL description of a CRS, but
rather of pieces of information (as axis order) that are useful for a
number of use cases, and that need to be accessible /.queryable via
SPARQL or, in general, with tools / applications not able to process
geospatial formats. I think this is very much in line with the goal of
enabling re-use of spatial data across platforms.

Another possible reason to have a (partial) RDF description of a CRS
is to provide links to the available representations (Proj4, GML, WKT,
GeoJSON, etc.). Something like what you can get (in a human readable
presentation) from Spatial Reference - see, e.g.:

http://spatialreference.org/ref/epsg/4326/

This would enable software agents to know which are the available
formats, and to retrieve the one(s) they are able to consume.

Andrea

PS: IMHO, the same considerations apply to geometry encodings / representations.


On Wed, May 20, 2015 at 8:17 AM, Krzysztof Janowicz <janowicz@ucsb.edu> wrote:
> I agree with Simon here. There will always be Linked Data 'leaf nodes' that
> will not (and do not have to) be triplified. If I recall correctly, the
> GeoSPARQL group had similar discussions. In almost all cases (I can think
> of), for instance, having a full RDF serialization of a complex polyline
> feature does not add any value (compared to WKT). This is even not about
> Linked Data versus Semantic Web reasoning, it is simply about the added
> value (or the lack of it).
>
> Best,
> Krzysztof
>
>
> On 05/19/2015 10:30 PM, Simon.Cox@csiro.au wrote:
>>
>> Raphaël: how is 'semanticizing' the description of CRS helpful? As Peter
>> and I have shown there are existing XML-based services that deliver the
>> entire EPSG CRS dataset in fully structured form (which covers the lat/lon
>> vs lon/lat issue Lars). Given that these services have reliable URIs (based
>> on the EPSG identifiers), contain links (to the component elements like CS,
>> Datum, Axis, etc), and are in an open format (GML/XML), we are already up to
>> about 4 1/2-star linked data.
>>
>> I'm a big fan of RDF and OWL, partly because of the scalability and
>> flexibility, and tool support. But there are some boundaries over which the
>> value add of RDF is vanishingly small, particularly if some 'linked data'
>> that is already available. I question whether effort is wisely spent here,
>> compared with some other parts of the puzzle which are much less evolved
>> right now.
>>
>> Kerry raised the issue of scope, and suggested that the goal should be
>> n-star linked spatial data. I agree, but we need to be clear that "linked
>> data" != "semantic web with full reasoning", so need to be careful about
>> balance here.
>>
>> -----Original Message-----
>> From: Svensson, Lars [mailto:L.Svensson@dnb.de]
>> Sent: Tuesday, 19 May 2015 9:51 PM
>> To: Raphaël Troncy; Cox, Simon (L&W, Highett); Taylor, Kerry (Digital,
>> Acton); eparsons@google.com; janowicz@ucsb.edu
>> Cc: public-sdw-wg@w3.org
>> Subject: RE: UCR issue: phrasing of CRS requirement(s)
>>
>> On Tuesday, May 19, 2015 10:09 AM Raphaël Troncy wrote:
>>
>>>>   Thanks Kerry - that's essentially the way I see it, if by "linked
>>>> data representation" you are implying RDF. I would like to ask those
>>>> people advocating a new CRS encoding in RDF, what this would be
>>>> useful for?
>>>
>>> Well of course, this is a very "niche" usage, but typical use cases
>>> are for getting an explicit semantic description of how a CRS has been
>>> built so that you can, for example, query for all CRSs that use a
>>> specific Datum, or, more simply, ask for the EPSG identifier
>>> corresponding to the URI of a CRS, etc.
>>
>> Another case would be to get information about lat/long vs. long/lat.
>>
>> Best,
>>
>> Lars
>
>
>
> --
> Krzysztof Janowicz
>
> Geography Department, University of California, Santa Barbara
> 4830 Ellison Hall, Santa Barbara, CA 93106-4060
>
> Email: jano@geog.ucsb.edu
> Webpage: http://geog.ucsb.edu/~jano/
> Semantic Web Journal: http://www.semantic-web-journal.net
>
>



-- 
Andrea Perego, Ph.D.
Scientific / Technical Project Officer
European Commission DG JRC
Institute for Environment & Sustainability
Unit H06 - Digital Earth & Reference Data
Via E. Fermi, 2749 - TP 262
21027 Ispra VA, Italy

https://ec.europa.eu/jrc/

----
The views expressed are purely those of the writer and may
not in any circumstances be regarded as stating an official
position of the European Commission.
Received on Wednesday, 20 May 2015 16:10:04 UTC

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