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Re: Geo in RDF (was Re: Censorship?)

From: Boris Villazón Terrazas <bvillazon@fi.upm.es>
Date: Tue, 16 Nov 2010 00:51:45 +0100
Message-ID: <4CE1C791.5040408@fi.upm.es>
To: Stuart Williams <skw@epimorphics.com>
CC: public-egov-ig@w3.org
Hi Stuart, all

On 15/11/2010 15:26, Stuart Williams wrote:
> Hello Boris,
>
> On 13/11/2010 15:11, Boris Villazón Terrazas wrote:
>> I only want to point out our ongoing work in the context of the 
>> GeoLinkedData [1], in which  we are working with geospatial data. 
>> Basically, we are using geo:lat/geo:long style of giving position in 
>> WGS84 coordinates. A geospatial resource, for example a 
>> geoes:Provincia, has a geo:geometry, and this geo:geometry consists 
>> of a set of geo:points , and each geo:point consists of geo:lat and 
>> geo:long. You can find a figure describing this at [2].
> I've got a minor question wrt to the use of geoes:order in the diagram 
> at [2]. It seems to be giving the ordinal position of a Point in a 
> LineString. It seems to me that there isn't a single value of 
> geoes:order which applies to a given point... it depends on what 
> LineString the point is being included in.
We use the order for drawing the lines on the map, and we need to do it 
in the right order. So, first, line from Point(x1,y1) to Point (x2,y2), 
then line from Point(x2,y2) to Point(x3,y3) and so on.
That's why we use the geoes:order

>> A specific example, the resource Albacete Provincia at [3].
>> Also, we have a browser at [4].
>>
>> I think this is related with the discussion.
>> We can provide further information regarding the conversion from GML 
>> to RDF we performed.
>
> I think that the details of your conversion are fairly clear in your 
> presentation at http://www.slideshare.net/boricles/geo-upmv14boris
Basically, the information from the Spanish Geographical Institute are 
stored in Oracle 11 databases, and the geometry information in a blob 
column.
We use the Oracle STO Util package [X]  for transforming the blob column 
value into GML.
Then, we use GeoTools [Y] and Jena [Z] for converting GML into RDF 
following the model described in the diagram at [2]
>
> What I am looking for is a *widely* adopted practice, perferably 
> backed/endorsed by a defacto or de-jure standards organisation. I 
> don't think I have found such a beast except for the case of Point 
> positions expressed as WGS 84 lat/long in which case there is 
> widespread community practice in the use of the "Basic Geo (WGS84 
> lat/long) Vocabulary" [a].
> [a] http://www.w3.org/2003/01/geo/
>
Our geometry points are compliant to geo: 
http://www.w3.org/2003/01/geo/wgs84_pos#
> For curves (LineStrings), surfaces(Polygons) and  Boxes (Envelopes), 
> the Geo OWL vocabulary at [b,c] which mirrors GeoRSS GML [d] seems to 
> me to come close to being something that a common practice might 
> develop around, however it does 'camp' in an opengis.org namespace 
> without obvious endorsement from the OGC (unless I missed finding 
> that, which is perfectly possible).
>
> [b] http://www.w3.org/2005/Incubator/geo/XGR-geo-20071023/#owl
> [c] 
> http://www.w3.org/2005/Incubator/geo/XGR-geo-20071023/W3C_XGR_Geo_files/geo_2007.owl
> [d] http://www.georss.org/gml#GeoRSS_GML
>
We have checked them, but at that time we prefer to follow the 
gml:LineString, however we can extend our model to include them.

> I think Gannon was making a point about localized re-invention of 
> vocabulary either being inevitable or maybe accidental - either way it 
> mitigates against the widespread adoption of a common practice and 
> potentially linits the reuse of data assets published using a 
> particular local practice. It also mitigates against tooling, 
> developing to support such things as spatial-indexes in SPARQL stores, 
> because without the use of common vocabularies you loose the triggers 
> that would induce index building - and responsive UIs seeking to 
> display artefacts within spatial bounding boxes could well do with the 
> help a spatial index could give.
Why don't all of us  start to collect the experiences we have to publish 
and consume geoespatial linked data?
Thoughts? suggestions?

Best

Boris

[X] SELECTTO_CHAR(SDO_UTIL.TO_GML311GEOMETRY(geometryColumn))

AS Gml311Geometry

       FROM "DB"."TABLE" c

       WHEREc.Name='Arroyo'

[Y] http://www.geotools.org/
[Z] http://jena.sourceforge.net/
>>
>>
>> geo: http://www.w3.org/2003/01/geo/wgs84_pos#
>> [1]: http://geo.linkeddata.es/
>> [2]: http://mccarthy.dia.fi.upm.es/challenge/example1.png
>> [3]: http://geo.linkeddata.es/page/resource/Provincia/Albacete
>> [4]: http://geo.linkeddata.es/browser/
>>
>
> BR
>
> Stuart
--
Boris Villazón-Terrazas
Ontology Engineering Group (OEG)
http://www.oeg-upm.net

Departamento de Inteligencia Artificial
Facultad de Informática
Universidad Politécnica de Madrid
Campus de Montegancedo, s/n
Boadilla del Monte - 28660 Madrid, Spain
Received on Monday, 15 November 2010 23:52:16 GMT

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