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Representations allow you to symbolize your data using a flexible, rule-based structure that is stored inside the geodatabase along with your data. Feature classes can support multiple feature class representations simultaneously, so a variety of map products can be derived from a single database without the unnecessary storage of copies of data. The representation of a single feature (called a feature representation) can be modified if necessary, creating a persistent override to the representation rule, which is also stored and maintained within the geodatabase. Representations provide the organizational structure of rule-based symbology while retaining the flexibility to customize the portrayal of individual features.
Feature class representations
A feature class representation is a property of a feature class that allows you to specify and store a series of rules that dictate the way the features in the feature class should be drawn. A feature class can have more than one representation, allowing the same data to be displayed in different ways for different purposes.
The easiest way to create a feature class representation is to convert the standard symbology of a feature layer in ArcMap to a feature class representation, which will automatically translate symbol categories into representation rules. Representation rules can then be added, removed, or modified as necessary.
Representations are managed as properties of their associated feature class. From ArcCatalog or the Catalog window in ArcMap, click the Representations tab on the Feature Class Properties dialog box to create, remove, or rename representations. Representation rules can be managed by accessing a feature class representation's properties. Alternatively, you can create feature class representations using the Add Representation geoprocessing tool.
How are representations stored?
Representations are a property of a feature class. Only simple feature classes can have representations. A feature class that resides in any type of geodatabase can have representations. Representations are implemented as a geodatabase workspace extension and managed by the geodatabase. Two fields are added to a feature class when a representation is created.
- The RuleID field is an integer field that stores a reference to the representation rule for each feature. The representation rules themselves are stored within the geodatabase system tables.
- The Override field is a BLOB field that stores feature-specific overrides to the representation rules.
A feature representation is the individual instance of a representation rule applied to a single feature. It is the graphic outcome of the sequence of geometric effects and symbol layers as applied to the geometry of the feature. If necessary, components of the appearance of a feature representation can be altered from its representation rule and stored as an override. This is typically done to resolve conflicts or otherwise fine-tune the depiction of a single feature.
Most properties of a representation rule can be modified for individual features by using the representation editing tools found on the Representation toolbar. These changes become overrides stored in the Override field in the attribute table or in an explicit field that was specified when the representation rule was established.
You can also change the geometry of feature representations in an edit session. Doing so will either create a shape override stored in the Override field or modify the shape of the feature in the source feature class (and within all representations associated with that feature class), depending on the editing behavior of the feature class representation. This setting can be changed by accessing the properties of the feature class representation on the Feature Class Properties dialog box in ArcCatalog or in the Catalog window in ArcMap.