In a complex data model, having sub-features representing relationships between features is often needed. For example, linking a device point table to a cable feature in an M-1 relationship (a cable can have multiple devices associated with it).

The same principle can be applied to any sub-feature type (point, line, polygon). In the example above, to produce the desired behavior, make sure not to specify any text field while registering this feature inside the OpenCities Geospatial Administrator. While OpenCities Map does not leverage this capability, you can take advantage of this data structure using the XFM APIs .