Validate topology and inspect topology properties

Although you haven’t changed the geometry of any features, you have changed the subtype of a couple of features. If a subtype of a feature class is specified in a topology rule, changing the subtype can create topology errors.

Validating a topology can sometimes take some time to complete, especially if you have made a large number of edits, you are working on large or complex datasets, or you have many topology rules. Validating the current extent saves time when you are trying to locate errors in a specific area.

The topology validation process identified an error within the area you’ve just been editing and marked it with a red error feature. Red is the default color for error features, although you can change the way they are symbolized.

You can investigate the properties of a topology to identify what could cause topology errors to be found. The Topology layer lets you view topology errors, as well as other information about the topology, in ArcMap.

The Feature Classes tab shows the feature classes in the dataset that participate in the topology. The Parcels feature class that's just been edited is one of two feature classes that participates in the topology; Blocks is the other.

The rules of the topology are listed on the Rules tab. A topology could be created with no rules or with as many as a dozen, or more, depending on the complexity of your data model.

The first rule in the list means that features within the feature class Parcels are bound by the Must Not Overlap rule. Parcels that overlap (for example, because of digitizing errors) will be discovered when the topology is validated.

Since the feature geometry wasn't edited, it is unlikely that the edits violated the Parcels Must Not Overlap rule. However, the second rule, ""Parcels: Residential Must Be Covered By Blocks: Residential" involves the Residential subtype of the Parcels feature class, which was edited.

This rule states that Residential subtype features in Parcels must be covered by Residential subtype features in Blocks.