Split and merge policies

When splitting or merging line or polygon features, you can use attribute domains to specify how attributes are handled after the split or merge. For instance, if a large parcel is being split into two smaller ones, do you want the new parcels to have the same attribute values as the original parcel or will the values need to be adjusted?

When you create attribute domains, you can define split and merge policies to manage attributes that will be affected by edits to a feature's geometry.

Split policies

When a feature is split into two new features, you can set the split policy to be duplicate, default value, or geometry ratio.

• Duplicate — both features inherit the same attribute value as the original feature.
• Default value — both features are assigned the default attribute value if one has been specified in the field properties (or subtype). If no default value has been specified, both features inherit the same value as the original feature.
• Geometry ratio — each feature is assigned a new attribute value based on a ratio of the original feature's attribute value.

When this parcel feature is split, the values in the three attribute fields reflect the results of the three different split policies.

Merge policies

When two features are merged into one, you can set the merge policy to be default value, sum, or weighted average.

• Default value — the new feature is assigned the default attribute value if one has been specified. If no default value has been specified, the feature will inherit the value of one of the originals.
• Sum — the new feature is assigned an attribute value that is the sum of the values of the original features.
• Weighted average — the new feature is assigned an attribute value that is the weighted average, based on geometry, of the values of the original features.

Implementing merge policies

To implement the merge policy set by an attribute domain, you will need to add a custom button to the Editor toolbar and use it instead of the standard Merge command, which you learned how to use in the previous module.

For instructions on adding this custom command, refer to the topic Merge features and respect merge rules, available from the ArcGIS Developer Online Web site.

When these agricultural parcels are merged, the values for the three attributes reflect the results of the three different merge policies.

Not all split and merge policy options are available for all field types. The table below summarizes the attribute domain types and their split and merge policy options.

	Field Types	Split Policy Options	Merge Policy Options
Coded Value Domain	Date, double, float, long integer, short integer, text	Default value, Duplicate	Default value
Range Domain	Date, double, float, long integer, short integer	Default value, Duplicate, Geometry ratio	Default value, Sum values, Weighted average