OGR and OpenGIS Simple Features for OLE DB
With the support of SoftMap and Safe Software an OLE DB provider on top of OGR has been implemented (circa 2002), attempting to adhere to the OpenGIS Simple Features for COM specification to the extent possible. This implementation is not certified as compliant with the OpenGIS specification.
While OGR can be used via the OLE DB interface, it can also just be called directly as a C++ library. OGR attempts to provide an OpenGIS Simple Features inspired terminology and view of datasets even when used in this fashion. Note that there is no OpenGIS specification for a C or C++ interface.
The OLE DB provider was migrated out of GDAL/OGR trunk in 2007 due primarily to issues with whether certain components were properly redistributable (see ticket #1817). The provider has not been actively maintained for a while, and currently it seems to be unbuildable due to incompatabilities with Microsoft's current ATL. However, the code is preserved under source control at http://svn.osgeo.org/gdal/spike/sfcom_oledb.
The only current GDAL/OGR developer with significant experience with the OLEDB provider is Frank Warmerdam who has relatively little interest in reviving it.