Relationship classes

In a geodatabase, relationship classes provide a way to model relationships that exist between real-world objects such as parcels and buildings or streams and water sample data. Relationship classes help make your GIS database more accurately reflect the real world and facilitate data maintenance.

For example, in the real world, buildings are always located on parcels. When the ownership of a parcel changes hands, the ownership of the buildings on the parcel usually changes as well. If a building footprint changes, it can affect the parcel (the value of the parcel improvements may increase or decrease). By setting up a relationship class between these two feature classes, you can help make sure that when a feature in one of the feature classes changes, related features in the other feature class are updated.

The relationships stored in a relationship class can be between two feature classes (such as buildings and parcels, top) or between a feature class and a nonspatial table (such as streams and water quality sampling data, bottom).

When you create a relationship class, you define the properties of the relationships. Recall in the first exercise of this module, when you deleted some lots from the subdivision, the homes located on the lots were also deleted automatically. This behavior between the related objects was controlled by a relationship property.

You can also create rules to maintain valid relationships. For example, you could set up rules that control how many buildings are allowed on parcels in different zoning areas.

Relationship classes are created in ArcCatalog. You will work with relationship classes in Lab 9.