Understanding representation overrides
This topic applies to ArcGIS for Desktop Standard and ArcGIS for Desktop Advanced only.
Feature class representations display the features of your data according to the properties established in representation rules. There may be times when it becomes necessary to make exceptions to these rules to depict the full diversity of your data, to resolve visual congestion, or to highlight special features. These exceptions, or overrides, can be made for individual feature representations during an edit session without disrupting the structure of the representation rule. Overrides should be used sparingly to keep your model simple and efficient; numerous overrides on a map is an indication that your current set of rules is inadequate and should be reevaluated.
In addition to overriding the display properties of representation rules, you can override the geometry of feature representations without affecting the spatial integrity of the supporting feature class. The alternate setting allows geometry edits to be reflected directly in the Shape field of the supporting feature class. This option is less commonly used, employed only in situations where a database is dedicated to cartographic output at a single scale, where you would want edits to appear in every representation made from that data.
In some cases, it will become necessary to obtain complete control over the display of a feature and disengage it from the representation rule altogether. The result is a free representation, for which you can alter the entire structure of the rule and even add new geometry elements.
Overriding representation properties
Each component of the symbol layers and geometric effects that compose a representation rule becomes a property of that representation rule. You can override the representation rule for individual feature representations by manipulating the values of these properties during an edit session.
You can choose a new value to override the default value for that property, or you can change some properties interactively (with WYSIWYG feedback) using the representation editing tools.
Overrides are not a property of the map layer. They are persistent, stored within the data just as representation rules, and will be reflected on any map that relies on the same feature class representation. It is easy to remove an override for a specific feature to return it to the symbology dictated by the rule. You don't have to break the rule to override it; other properties will still get updated if the rule changes, even if an override is present. The overridden property will remain as is until you manually change it or remove the override.
Representation property overrides
A representation property may be followed by an icon in the Representation Properties window while editing that indicates its current state.
The representation property references a field in the feature class table.
The representation property has been overridden from its default value. Clicking the icon will remove the override and return the property to the default value specified in the representation rule.
The representation property references a field in the feature class table, and its value is different from the default value specified in the representation rule. Clicking the icon will change the value in the field to NULL and have the property follow the default value specified in the rule.
Overriding representation geometry
When you create a feature class representation, you must specify its geometry editing behavior to determine what will happen when you edit feature representations with the representation editing tools. Either you will directly edit the shape itself (as you would in a standard edit session) or you will create and store a copy of a changed feature in the Override field of the feature class representation. That is, you must choose whether you will alter the source geometry of the supporting feature class (and all its derived feature class representations) or save secondary versions of geometry that get used for display only when that feature class representation is active and won't be recognized by the supporting feature class.
This decision will be guided by whether you have a database that has already been processed and is intended for display only (often called a digital cartographic model [DCM]), or whether you are working with a master source database whose spatial integrity must be maintained for future analysis or processing (a digital landscape model [DLM]). The reasons to choose one option over the other will depend on how your cartographic data is managed and what your organization's workflow is. Before you begin map finishing, you should have a clear idea of how you want to model your data, who will have access to change the structure of your database, and how you will handle updates to your spatial data.
This setting is a property of the feature class representation that is specified when it is created. See Managing the geometry editing behavior setting for more information on choosing an appropriate geometry editing behavior for your project.
Overriding with free representations
In instances where you need full graphic control over the appearance of a single feature, you can fully override it by converting it to a free representation, which allows you to, among other things, break the representation symbology down to access its graphic primitives and edit those individually. It also allows you to alter not just the representation properties but also the structure of the representation rule itself and to add new graphic shapes that aren't derived from geographic geometry. Even more so than with representation rule overrides, free representations should be created sparingly, as they require the storage of information in the Override field and can, therefore, affect performance when many are used on one map.