Hi,

The Open Geospatial Consortium (OGC) are forming a Standards Working
Group to develop a Geographic Linkage Service.

I was involved in the OGC Geolinking Interoperability Experiment last
year that developed a draft specification. In this we developed a client
and server. I am part of a team still working on this now, but more on
the security and service side. We are looking to keep track of this
moving target (the specification) and I would like to contribute our
effort to the GeoTools code base in due course if that seems sensible.
In the meantime I am setting up a source forge project GeoLynx
(http://sourceforge.net/projects/geolynx/). Sorry there is no code there
yet that you can use.

Best wishes,

Andy
http://www.geog.leeds.ac.uk/people/a.turner/
 
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
Jody Garnett
Sent: 04 September 2008 15:37
To: Milton Jonathan
Cc: [email protected]
Subject: Re: [Geotools-gt2-users] Linkning features to external data

Milton Jonathan wrote:
> Hello people
>
> I have a (common?) practical problem where I have spatial data (with 
> some attributes) on one side (e.g., a shapefile, or a spatial table in

> a database), and a bunch of related information that's being stored 
> somewhere else (e.g., a regular table in a database that has an FID 
> column matching those in the spatial table).
>
> So I ask: what is the most usual way in GeoTools for "glueing" or 
> linking these two sets of data?
Brute force and a for loop :-)  If you need to join on spatial data take
one data set and stuff the geometries in a JTS Spatial index to save
time. If you can do it based on ID then a HashSet will be your friend.

If you check into the validation module you can see lots of painful slow
examples of doing things this way.
> table). I guess that, when everything is within a single database, one

> can create a view that already joins these data beforehand, and the 
> feature source would then be that view. Or is there a better way of 
> doing this?
>   
Correct; that is a common solution when the data is in the same
database.
> Anyway, I am not sure if this is really within the scope GeoTools 
> itself, but it looks like a very common problem and so maybe someone 
> has already thought of some mechanisms in GeoToools to help with
that..
>
>   
It is in scope and there have been a few attempts at solving it - but
nothing successful so far. The author of JTS Topology Suite has a pretty
interesting project in this regard (a small domain specific language
that supports joins and stuff) - but you can go ask about that on the
JTS email list cause I do not have the details.

My best solution would be to load stuff into a local H2 database and
hack away; but I am waiting for someone bright to add a spatial index to
H2 before even trying that.

Jody

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