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

Andrea,

On Wednesday, May 20, 2015 6:09 PM Andrea Perego wrote:

> 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.

Yes, that is what I was looking for.

> 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/


Hmm, yes sort of. Interesting to see that the axis order is not mentioned on that page. I keep coming back to that since I struggled a bit with axis order when converting the coordinates in our linked data service to WKT...

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

Best,

Lars
> 
> 
> 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 Thursday, 21 May 2015 08:44:56 UTC