[postgis-users] Shared geometries?

[Stephen Woodbridge]

Jeff Dege wrote:
> Suppose I have a shapefile containing county data, with polygon
> geometries representing the county boundaries.  And another shapefile
> containing state data, with polygon geometries representing the state
> boundaries.
> 
> The state boundaries and the county boundaries should coincide, though I
> know of no way of enforcing that with shapefiles.
> 
> Is there a way, in PostGIS, to create two layers that have different
> sets of attributes, but whose gemoetries share the same points?  So that
> if I edit the county boundaries, the state boundaries will automatically
> reflect those changes?

Jeff,

This is really a topology problem in the more general sense. Think of a 
road the crosses the state boundary, you want that noded at the boundary 
also.

There is no generalized way to do this today in postGIS. You can 
certainly create you own tables and view that share geometry have have 
different attributes. But you would have to manage all the interactions 
and relationships on you own. You can probably set up tigers to do a 
bunch of the work.

-Steve