[GRASS-user] Modelling 1:n and m:n relationships in GIS

Markus Metz markus.metz.giswork at googlemail.com
Tue Mar 10 07:57:03 EDT 2009

I have updated the vectorintro (vector/vectorintro.html) in grass64, 
grass65 and grass7.  "Attribute management" has been changed to "Vector 
object categories and attribute management".

Please check for and report any errors/inconsistencies or if the changed 
description is incomprehensible.

Markus M

Benjamin Ducke wrote:
> Dear all,
> I keep getting into situations where mapping 1:n and m:n relationships
> in relational DBMS to GIS vector models becomes a problem.
> The toughest restrictions of course are the 1:1 relation between map
> features and attribute table records and the fact that GIS relates
> data by spatial overlay, not foreign fields. I realize that some GIS
> (like GRASS) are somewhat more flexible in that they can attach more
> than one attribute table to a layer, but I am really looking for more
> portable ways to deal with this.
> - How do you deal with 1:n and m:n relations in GIS?
> - What do you do if there are no spatial representations for the
> records on the "n" side? Can that be handled at all?
> Apparently, it would be possible to model some of this using overlapping
> features in Shapefiles, but that would violate topology rules.
> Any ideas are very welcome, indeed!
> Thanks, everyone, 
> Ben

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