Hi, This is a call for discussion for "RFC 41 : Support for multiple geometry fields in OGR" :
http://trac.osgeo.org/gdal/wiki/rfc41_multiple_geometry_fields As an introduction, you'll find below the first paragraphs of the RFC. Much more to read at the above link ! == Summary == Add read/write support in the OGR data model for features with multiple geometry fields. == Motivation == The OGR data model is currently tied to a single geometry field per feature, feature definition and layer. But a number of data formats support multiple geometry fields. The OGC Simple Feature Specifications also do not limit to one geometry field per layer (e.g. §7.1.4 of [http://portal.opengeospatial.org/files/?artifact_id=25354 OGC 06-104r4 "OpenGIS® Implementation Standard for Geographic information - Simple feature access -Part 2: SQL option]). There are workarounds : using geometries of type GEOMETRYCOLLECTION, or advertizing as many layers as there are geometry columns in the layer (like currently done in the PostGIS or SQLite drivers). All those approach are at best workarounds that suffer from limitations : * GEOMETRYCOLLECTION approach : no way to know the name/semantics of each sub-geometry. All sub-geometries must be expressed in the same SRS. No way of guaranteeing that the GEOMETRYCOLLECTION has always the same number of sub-geometries or that there are of a consistent geometry type. * one layer per geometry column approach : only appropriate for read-only scenarios. Cannot work in write scenarios. The purpose of this RFC is to make support for multiple geometry fields per feature to be properly taken into account in the OGR data model. [...] Best regards, Even -- Geospatial professional services http://even.rouault.free.fr/services.html _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
