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| GeoCommunity Mailing List |
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| Subject: | Re: [gislist] Spatial Query Language |
| Date: |
04/05/2005 03:10:02 PM |
| From: |
Frank Warmerdam |
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On Apr 5, 2005 3:52 PM, Landon Blake <lblake@ksninc.com> wrote:
> I'm in the midst of planning 2 separate open source spatial database solutions. In both I will need to support spatial queries. I would like to implement a common standard in both.
>
> I'm looking for an official specification for a spatial query language, but have been unsuccessful so far. I found little tidbits with an on-line websearch but nothing concrete. I ran into one commercial solution: GEO/SQL. Is there an open standard for a spatial query language that I'm completely missing, or do most GIS users implement a homegrown or commercial solution?
Landon,
The obvious choice is the OpenGIS (er Open Geospatial?) Simple
Features for SQL specification. It defines a variety of spatial SQL
operators.
I would suggest you visit the OGC web site to see what products claim
conformance to it. The one I am familiar with is the PostGIS
extension to PostgreSQL which I believe does a fairly complete
implementation of the specification. Spatial queries are very efficient
but some other spatial operators (ie. buffering, overlay, etc) are not
exceptionally efficiently done. But I believe it is a pretty complete
implementaton of the spec, and it also has some extensions beyond
the spec. While it is an open source product, you can purchase
commercial support from Refractions, the creators.
http://postgis.refractions.net/
I would warn you that the specification has different levels of conformance,
and some vendors claim conformance while only doing the base level
which does not include the spatial SQL operators.
The other standard of note in this area is SQL MM, but I am not
personally aware of any implementations of it, nor do I have any
direct experience with it. SQL MM is an ISO specification.
Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for Rent
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