Hello,
Im working on a way to use D2RQ together with PostgreSQL/PostGIS functions
at the moment. I also had the problem that the spatial columns were not
recognized and got the message Unsupported database type code (1111)for
column planet_osm_point.geo while starting the D2R Server.
I let PostGis convert the data into the EWTK (Gives also the SRID of a
geometry back, I would guess that Oracle has similar functions) format using
this mapping:
map:planet_osm_point_geo a d2rq:PropertyBridge;
d2rq:belongsToClassMap map:planet_osm_point;
d2rq:property vocab:planet_osm_point_geo;
d2rq:sqlExpression "ST_AsEWTK(planet_osm_point.geo)";
In order for D2RQ to recognize the database type I had to add case
Types.OTHER: return TEXT_COLUMN; to the public int columnType(Attribute
column) method of the class BindingMaker.java. It is not the most elegant
way, but worked for my tests. If Oracle does not support the EWTK format,
maybe try a direct mapping like this:
map:planet_osm_point_geo a d2rq:PropertyBridge;
d2rq:belongsToClassMap map:planet_osm_geo;
d2rq:property vocab:planet_osm_polygon_point_geo;
d2rq:propertyDefinitionLabel "planet_osm_point geo";
d2rq:column "planet_osm_point.geo";
D2R Server gave me back the same textual values as PostGIS itself.
Kind Regards,
Thomas Günther
From: Randen, Yke van [mailto:[email protected]]
Sent: Mittwoch, 29. Juni 2011 17:25
To: '[email protected]'
Subject: [d2rq-dev] Mapping Oracle Spatial fields using D2RQ
Dear Sir
Im investigating the possibilities of your D2RQ product to make some data
from our Oracle database available for Sparql end points. I have selected
some tables for test purposes. These tables contain the Dutch highways
segments and the Dutch railroad segments. Beside normal attributes (date,
string and numerical) these tables also contain spatial attributes (Oracle
Spatial columns).
Until now i have successfully converted these tables into triplets, stored
them back in our Oracle database and queried them using Joseki, Jena under
Oracle Weblogic server and also using your D2R server. And i must say your
tool did a fantastic job (easy to use, easy to configure). However until now
i have not been able to convert the spatial data. In the tests so far i
removed the mapping for the spatial column from the mapping file.
I managed to create a workaround by converting the spatial columns to the
OGC Well Know Text format (using standard Oracle spatial functions) and use
that in the mapping. It works fine however i lack data about the coordinate
system (is it degrees as WSG84 or something else), and since Im not able to
define my geometries as subclasses of the standard OGC curve class reasoners
dont recognize it as geometries and therefore do not apply spatial
functions to those triplets.
Can you suggest to me how i can map my spatial columns to a class (which is
a subclass of Curve (http://www.w3.org/2003/01/geo/wgs84_pos)) and then
create triplets using your tool.
We would like to use this so we can make more data available as ontologies
and allow users to not only query normal attributes but also spatial
attributes.
Yours sincerely
Yke van Randen
CGI Ruimtelijke Modellen en Kennissystemen
Kamer C 106
+ Postbus 47
6700 AA Wageningen
H Droevendaalsesteeg 3 (gebouw 100)
6708 PB Wageningen
( +31 (0) 317 481828
Ê +31 (0) 317 419000 (fax)
e* mailto: <mailto:[email protected]> [email protected]
ü
<http://www.alterra.wur.nl/UK/research/Specialisation+Geo-information/>
http://www.alterra.wur.nl/UK/research/Specialisation+Geo-information/
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