openlink
Virtuoso is always changing the GeoSPARQL geometry type to the Virtuoso specific one when loading data
Consider the following triples and load them into a Virtuoso installation:
@prefix gsp: <http://www.opengis.net/ont/geosparql#> .
@prefix schema: <http://schema.org/> .
@prefix geo: <http://www.w3.org/2003/01/geo/wgs84_pos#> .
@prefix locn: <http://www.w3.org/ns/locn#> .
@prefix dul: <http://ontologydesignpatterns.org/ont/dul/DUL.owl#> .
@prefix dc: <http://purl.org/dc/elements/1.1/> .
<http://data.linkedevents.org/location/028f1b02-d121-46f9-bff7-b5e5509a356c/>
a dul:Place ;
rdfs:label "Duomo di Milano - Duomo of Milan" ;
dc:identifier "345483388889753" ;
dc:publisher <http://www.facebook.com> ;
schema:image <https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-xpa1/t31.0-8/s720x720/901621_475672112537546_754871748_o.jpg> ;
schema:interactionCount "3964 Checkins" , "3996 Likes" ;
schema:url <http://www.duomomilano.it/it/> ;
geo:location <http://data.linkedevents.org/location/028f1b02-d121-46f9-bff7-b5e5509a356c/geometry> .
<http://data.linkedevents.org/location/028f1b02-d121-46f9-bff7-b5e5509a356c/geometry>
a geo:Point ;
geo:lat "45.463925903103"^^xsd:double ;
geo:long "9.1927945677761"^^xsd:double ;
locn:geometry "POINT(9.1927945677761 45.463925903103)"^^gsp:wktLiteral .
Regardless of how this data is loaded into Virtuoso, we always get the following behavior which is the transformation of the triple
<http://data.linkedevents.org/location/028f1b02-d121-46f9-bff7-b5e5509a356c/geometry>
locn:geometry "POINT(9.1927945677761 45.463925903103)"^^gsp:wktLiteral .
into
<http://data.linkedevents.org/location/028f1b02-d121-46f9-bff7-b5e5509a356c/geometry>
locn:geometry "POINT(9.1927945677761 45.463925903103)"^^<http://www.openlinksw.com/schemas/virtrdf#Geometry>.
Why does Virtuoso change on the fly the GeoSPARQL datatype being used in the data by its own specific datatype? One can see this behavior when DESCRIBE-ing this resource or by simply running this query (see the results):
SELECT *
WHERE {
<http://data.linkedevents.org/location/028f1b02-d121-46f9-bff7-b5e5509a356c/geometry> ?p ?o
}
This issue seems also related to #195 #274 #295 and very recently #455. In several of those issues, all commenter have reported that they (must?) use the datatype virtrdf:Geometry. We do expect instead to use the GeoSPARQL datatype gsp:wktLiteral which is later on a pre-condition for some interlinking tools such as SILK to work.
This is really a blocker for us too. This issue is still not resolved in the latest Virtuoso release. @HughWilliams do you know when it will be resolved?
@rtroncy: Will have to check with development as to when this is scheduled to be fixed ...