Common topology tasks

This topic applies to ArcEditor and ArcInfo only.

A number of modifications can be made to a topology. In some cases, such as when renaming a topology, the change has no effect on the state of the topology. However in other cases, the change may require that the topology be revalidated. For example, changes such as adding new feature classes or rules or changing the cluster tolerance may create new dirty areas and error features and necessitate that the topology be revalidated.

Adding a new feature class to a topology

Using the Catalog window or ArcCatalog

Here are the steps to add a new feature class to an existing topology using the Catalog window or ArcCatalog.

1. Right-click the topology and click Properties.
2. Click the Feature Classes tab.
3. Click Add Class.
4. Click the feature class that you want to add to the topology and click OK.

   Only feature classes that are within the feature dataset and are not currently participating in a topology or geometric network can be added.

5. Set the coordinate rank for the added feature class.
6. Add any additional rules.
7. Click OK.
8. Validate the topology.

Using geoprocessing

You can also use geoprocessing topology tools to add feature classes and rules to an existing topology. Two tools are available in the Topology toolset in the Data Management toolbox:

• Add Feature Class To Topology
• Add Rule To Topology

Modifying a topology

A number of modifications can be made to a topology. In some cases, such as when renaming a topology, the change has no effect on the state of the topology. However, in other cases, the change may require that the topology be revalidated. For example, changes such as adding new feature classes or rules or changing the cluster tolerance may create new dirty areas and error features, and the topology must be revalidated.

Using subtypes in a topology

When you design a geodatabase, you should be aware of the options for using feature class subtypes in your topology.

About subtypes

Subtypes allow you to model real-world objects more effectively by building subclasses of the features within a feature class. For example, in a parcel feature class, you might have subclasses of normal parcels (which cannot overlap) and condo parcels (which are allowed to overlap). Further, the default value for zoning might be different for each parcel subtype (for example, Single Family residential versus Multifamily residential).

To learn more about subtypes and the geodatabase, see A quick tour of subtypes.

Subtypes within a topology

Subtypes in topologies can have different rules applied to each subtype as well as different coordinate ranks. This allows you to create rules that apply only to specific subtypes, for example, structures built before the subdivision was created.

For example, consider building footprints—you could model a situation where a small percentage of buildings legitimately cross parcel boundaries by creating subtypes of buildings and only creating the Must Be Covered By rule for the subtypes that cannot extend across a parcel.

You could also apply different coordinate ranks to each subtype. For example, parcels whose boundaries were entered using COGO tools might have a higher coordinate rank than other parcels in a different subtype that were entered using digitizing.

Removing a feature class

In the Catalog window, do the following:

1. Right-click the topology and click Properties.
2. Click the Feature Classes tab.
3. Click the feature class you want to remove.
4. Click Remove.
5. Click OK.

Renaming a topology

In the Catalog window, do the following:

1. Right-click the topology and click Properties.
2. Click the General tab.
3. Type a new name.
4. Click OK.

Note:

Renaming a topology does not affect its state, and the topology need not be revalidated.

Changing the cluster tolerance

In the Catalog window, do the following:

1. Right-click the topology and click Properties.
2. Click the General tab.
3. Type a new cluster tolerance value.
4. Click OK.

Note:

Changing the cluster tolerance of a topology will require that the topology be revalidated. The larger the cluster tolerance, the greater the likelihood that features in your data will be moved from their current positions. If the cluster tolerance is too large, the shapes will change.

Changing coordinate ranks

There are a number of ways to change rank settings in a topology.

Changing the number of ranks

1. Right-click the topology and click Properties.
2. Click the Feature Classes tab.
3. Type a number of ranks.
4. Click OK.

A topology can support up to 50 ranks to which feature classes may be assigned.

Note:

Changing the number or ranks alone will not require the topology to be revalidated.

Changing the rank of a feature class

1. Right-click the topology and click Properties.
2. Click the Feature Classes tab.
3. Click and change the current rank of the feature class.
4. Click OK.

Note:

Changing the rank of any feature class requires the topology to be revalidated.

Working with topology rules

There are many tasks to work with rules within a topology. You can do the following:

• Add or remove rules from an existing topology.
• Save rules as a rule set file that can be shared and reused.
• View rule descriptions and diagrams.

Adding rules to a topology

1. Right-click the topology and click Properties.
2. Click the Rules tab.
3. Click Add Rule and choose the rule.
4. Click OK on all dialog boxes.

Note:

After adding a new rule, you must revalidate your topology.

Removing a rule from a topology

1. Right-click the topology and click Properties.
2. Click the Rules tab.
3. Click the rule that you want to remove.
4. Click Remove.
5. Click OK on all dialog boxes.

Note:

Removing a rule will require the topology to be revalidated.

Saving topology rules to a Rule Set File

1. Right-click the topology and click Properties.
2. Click the Rules tab.
3. Click Save Rules.
4. Navigate to where you want to save the rules that you've defined for the topology.
5. Type a name.
6. Click Save to save all the rules for the topology to the file.
7. Click OK.

Loading topology rules from a Rule Set File

1. Right-click the topology and click Properties.
2. Click the Rules tab.
3. Click Save Rules.
4. Click Load Rules.
5. Navigate to the place where the rule set that you want to load is saved.
6. Click the rule set.
7. Click Open.

   If the rule set was created from a topology that had the same feature class names as the feature classes in the new topology you're defining, the feature classes named in the rule set should be correctly matched to the feature classes in the new topology. If the names are different, you will need to match the feature classes mentioned in the rule set to their corresponding feature classes in the new topology.

8. For each source feature class that is not mapped, click in the Target column and click the feature class to which it corresponds in the new topology.
9. Click OK on all dialog boxes.

Note:

Loading a Rule Set into a topology with previously specified rules will append the rules from the Rule Set to the existing rules.

Note:

Loading a Rule Set will require the topology to be revalidated.

Note:

If there are feature classes specified in a rule set that cannot be matched to feature classes in the new topology, rules involving the unmatched feature classes will not be loaded.

Summarizing topology errors

You can view a summary of the number of errors in a topology from the Topology Properties dialog box. The summary tells you how many errors and exceptions exist for each of the topology rules.

You can save the summary as a text file to create a record of the state of the topology at a given time. This can be a useful way to document and monitor progress on a large topology editing project.

Querying and navigating a topology graph

The ArcGIS developer tools provide programmers with access to the topology graph, which is a planar representation of the geometries in the feature classes participating in a topology. For more information on working with the topology graph, see the ArcObjects Help for .NET.