[Java-collab] Re: Collab on Geometry

[Markus Schneider]

Hello Mark,

Mark Leslie wrote:

> I'm curious what you're aiming for here.  SFSQL and SQL-MM both define
> their own (somewhat flawed) WKB formats, and PostGIS's EWKB is an
> attempt to find a happy middleground between the two that is actually
> useful.  But these only store the geometries and some metadata in a
> single binary blob.  My first read of this had me convinced that you
> were looking for a binary representation of the entire feature.  What
> are you looking to accomplish?  Is this hoping to be an extension of
> some WKB type to handle the geometry structures defined in GML?

the idea was born out of the wish to store GML geometry structures faithfully in today's spatial databases (PostGIS,
Oracle Spatial, ...) with their rather limited set of geometry types. We're already using a similar approach
successfully to store linearized curves as PostGIS linestrings and put a text field beside it that keeps the GML
representation (as XML) of the original geometry. This way, our WFS can evaluate queries based on the native PostGIS
geometry and return the original GML in the response (as the value of the geometry property). This works pretty well,
but has obvious disadvantages.

A major improvement would be to store the original geometry in a binary format. Probably, this format
whould somehow be related to EWKB. Another issue that may have implications on the binary encoding is our wish to
support the storage of identifiable (gml:id) sub-geometries and references to other geometries (xlink:href).

Any help on finding a suitable encoding is welcome...

Best regards,
Markus

-- 
Markus Schneider

l a t / l o n  GmbH
Aennchenstrasse 19           53177 Bonn, Germany
phone ++49 +228 184960       fax ++49 +228 1849629
http://www.lat-lon.de        http://www.deegree.org

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