Designing a geodatabase topology
This topic applies to ArcEditor and ArcInfo only.
You can work through several design steps prior to developing a topology design before you use ArcGIS to create a topology in the geodatabase.
- Make a list of the desired feature classes that will share geometry.
- Specify the spatial representations of each feature class (point, line, or polygon).
- List the feature classes that will share geometry and will be edited and maintained together. For example, if you perform an edit on the geometry of one of the features, the others will be updated as well.Some feature classes commonly managed in a shared topology
Examples of feature classes that participate in topologies
Subsample of topology rules
Parcel polygons, Parcel boundaries (lines), Parcel corners (points)
Parcel polygons must not overlap. Parcel polygon boundaries must be covered by Parcel boundary lines. Parcel boundary endpoints must be covered by Parcel corner points.
Street centerlines and census units
Street centerlines, Census blocks, Census block groups, Census tracts
Street lines must not intersect or touch interior. Census blocks must not overlap. Census block groups must be covered by census blocks. Census block groups must not overlap. Census tracts must be covered by census block groups. Census tracts must not overlap.
Soil type polygons
Soil polygons must not overlap. Soil polygons must not have gaps.
Hydro lines, Hydro points, Watersheds (polygons)
Hydro lines must not self-overlap. Hydro points must be covered by hydro lines. Watersheds must not overlap. Watersheds must not have gaps.
- Organize these feature classes into a feature dataset.
- Specify topology rules between the elements in each individual feature class. For example, parcels can be single-part or multipart polygons. Adjacent parcels share geometry. Parcels cannot overlap.
- Specify the topology rules between feature classes. For example, the lines that define parcel polygons must be covered by parcel boundary lines.
- Identify the accuracy ranks of the coordinates in each feature class. The most accurate feature classes should receive a rank of 1, and lower accuracies must descend in order from the highest rank (the second most accurate gets a rank of 2 and so on). Multiple feature classes can have the same accuracy rank. If you cannot perceive that there is a difference in accuracy, set the ranks of all feature classes to 1 (in other words, so the accuracy is the same).
- Build a test geodatabase (using a file or a personal geodatabase) with a copy of your features to test your proposed topology design. Exercise your prototype geodatabase. For example, add a topology based on your proposed design, validate it, and edit some of the features. This will give you insight into behavior and help you refine your design.
- Refine and adjust your design until you have a working implementation.
A book from ESRI Press named Designing Geodatabases: Case Studies in GIS Data Modeling by David Arctur and Michael Zeiler provides some examples. Also see http://support.esri.com/datamodels.