Relationships and ArcGIS

This topic applies to ArcEditor and ArcInfo only.

A GIS integrates information about various types of geographic and nongeographic entities, many of which can be related.

• Geographic entities can relate to other geographic entities. For example, a building can be associated with a parcel.
• Geographic entities can relate to nongeographic entities. For example, a parcel of land can be associated with an owner.
• Nongeographic entities can relate to other nongeographic entities. For example, a parcel owner can be assigned a tax code.

ArcGIS provides many ways to associate features and records with each other in a geodatabase. When setting up relationships between geographic features, the first step is to model the spatial relationships between features. Consider how you can use geodatabase topologies, geometric networks, shared-edge editing, geometry snapping during editing, and geospatial operators in your data model. These methods help you efficiently create and maintain data.

If you need to capture relationships among features that are in close proximity, but there is ambiguity about the association from the spatial context, you can't use spatial relationships alone. For example, a pad-mounted transformer may serve electric power to several buildings, but unless you have the secondary lines mapped, you can't have a clean, unambiguous association between a transformer and the set of buildings it serves.

Another scenario for which you won't be able to set up a spatial relationship is if the association includes a nongeographic entity, such as one or more parcel owners.

For these two general cases, you can set up attribute relationships within your relationship classes, use on-the-fly relates, or create joins. These methods provide a connection between records in one class (feature class or table) and those in another.