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From Paolo Castagna <>
Subject Re: Jena and PostGIS (à la LARQ)
Date Tue, 13 Sep 2011 14:52:57 GMT
Hi Alex

Alexander Dutton wrote:
> Hash: SHA1
> Hi all,
> We've currently got a lot of (simple) geospatial data in
> <> (served behind the scenes by Fuseki).
> We'd like to do some geospatial indexing magic, and were wondering
> about writing something a bit like LARQ that will pull out things like
> geo:Points and WKT literals, place them in a PostGIS-flavoured DB, and
> then implements something like GeoSPARQL (<>).

Which kind of queries you would like/need to run?

The use cases I've seen (on the job) are often quite simple, since users
are not GIS expert. The vast majority of them can be reduced to:

  - searching near by a point (often sorting results by distance)
  - searching within a bounded box

Ideally, it would be good to have something pure Java which keeps
things very simple to install. Ideally, zero installation cost:
download, unzip, load data, run (as it is for Fuseki).

What would be the best way to integrate|use such extensions into Fuseki?
Ideally, with 0 changes to Fuseki code base... is that currently possible?

Also, I have not been following the progress around GeoSPARQL:
... is there anything interesting/relevant there? Code? :-)

Finally, things to think about are:

  - how to you initially build your geo indexes?
  - how you keep those indexes up-to-date as you add/remove triples|quads?
  - how do we plug-in|use|integrate this from|into ARQ (or TDB or Fuseki)?

Currently, I am not completely satisfied by how we|I do this with LARQ
(via assemblers), but maybe it's just because I am not an Jena's assembler

Ideally, I'd like to have a way to add property functions to ARQ (and use
them with TDB datasets or Fuseki) without changing ARQ or TDB nor Fuseki
source code. You drop a jar in your class path and the property function
as well as keeping indexes up-to-date is there.


> Has anyone started doing this or something similar? I'm happy to give
> it a go and I'm sure my employer would be happy to contribute it back
> to Jena and the ASF. My plan was to go through the LARQ codebase to
> work out how it hooks itself in, and use that as a model.
> Yours,
> Alex
> - -- 
> Alexander Dutton
> Metamorphoses Project Developer, Claros
> Oxford University Computing Services, ℡ 01865 (6)13483
> Version: GnuPG v1.4.11 (GNU/Linux)
> Comment: Using GnuPG with Fedora -
> 38oAnR5n+oi1nuTZAfRdOrF2mcOac2Ck
> =r1dj

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