OpenGIS

I am a technical representative to the Open GIS Consortium on behalf of Chesapeake Analytics. I have been reviewing documents and have decided it would be worthwhile to attempt to provide OpenSource reference implementations of some of the OpenGIS technology specifications.

Beyond the goals of advancing OpenSource, and OpenGIS standards, my reasons also include developing a solid understanding of OpenGIS standards, and technology so that I can propose OpenGIS related projects to various clients. I am trying to get a prototype running so that I can more accurately bid those contracts, and to prove that I have the required expertise.

Simple Features

I have started work aimed at implementing a Simple Features for COM (SFCOM) server. The reference server would likely provide access to Shapefiles using my Shapelib, but I hope that the implementation would provide a useful set of sample code for others other servers.

I picked SFCOM over SFCORBA because it seems like the Windows technology will be more used. However, I am interested in pursuing an SFCORBA implementation using a free ORB like MICO at some point in the future. I haven't pursued SFSQL because I haven't got (nor could I afford) access to Oracle, SDE or another database backend that I could build on. Perhaps at some point in the future it could be done within PostgreSQL, but I think it would be a big job.

Current Status

Downloaded and installed MSDASDK, and successfully built and ran sample OLE DB producer and consumer.
Downloaded sample datasets for conformance testing of SFCOM implementations (in MS Access format) from OGC (these were provided to OGC by Cadcorp).
Developed core C++ classes for modelling some of the simple feature data types (Point, LineString (Curve/LinearRing), and Polygon), and capable of converting back and forth between well known binary format, and object instances. This core is known as OGR (OpenGIS Reference subsystem). The ogr_geometry.h file shows the classes represented.
Developed OLE DB consumer (client) code capable of reading geometry columns (BLOBs in well known binary (WKB) format) and converting them to object instances. This consists principly of sfdump.cpp, oledb_sup.h and oledbsuprowset.cpp.
Installed Visual Basic, and the Cadcorp producer, client and test suite. The cadcorp provider and geometry service pass the cadcorp test suite.
My client program has been updated to read binary data from the Cadcorp provider using the IStream interface (the column appears as type DBTYPE_IUNKNOWN). However, the client doesn't get the correct binary data for records after the first.
My client program has been updated to use the Cadcorp geometry services to interpete the BLOB data, but I always get an invalid argument error in the CreateFromWKB() method on the IGeometryFactory. This appears to be related to the BLOB VARIANT argument.
I have begun implementing a Geometry service. The code builds and works at least for building a IPoint geometry from a blob, and fetching the point coordinates back from it. This service uses the objects defined in ogr_geometry.h to do the hard stuff.

Resources

SFCOM Notes: hard won tidbits of knowledge.
SFCOM Developers Mailing List

Plans

Evolve my client to work aginst the OLE DB support inherent in the Cadcorp OLE DB producer, including some of the table navigation information specific to OpenGIS. (The current SFDUMP program requires the user to provide the name of the geometry column name in the table). (Underway)
Once this is all working, I would launch into implementation of SF COM services myself. Initially I will continue to use MS Access to provide the OLE DB functionality, but implement my own copy of at least some of the SF COM Geometry services based on the OGR library. (Underway)
Following this, I would attempt to actually implement an OLE DB interface to the Shapelib API, making shapefiles appear to be a proper database. (Being pursued by Ken Shih).