You can create new representations for a feature class in ArcCatalog. In ArcMap, the Layer Properties provides the symbology information for the new representation, while in ArcCatalog, the information about symbology is derived from a layer file. You can create layer files for your feature classes with symbology of your choosing for those times when you want to create representations in ArcCatalog. In ArcCatalog, you can do this with ModelBuilder, at the command line, with a script, with the Add Representation tool, or through the Feature Class Properties dialog box.

To create a feature class representation in ArcCatalog, right-click the feature class in the Catalog tree and click Properties. Click the Representations tab on the Feature Class Properties dialog box. In this example the list is empty because the RoadP feature class does not have any feature class representations. To add one, Click New. This will open the New Representation wizard. Note the similarities between this dialog box and the Convert Symbology to Representation dialog box in ArcMap.

You can import rules from any layer file. After you check this box you can choose where your representation rules come from. When the layer file you are importing rules from has the same source as the current feature class, you can also check the box to Assign rules to the features that match the layer file. This will assign representation rules to individual features. When you're done, click Finish.

The new feature class representation appears on the Representations tab of the Feature Class Properties dialog box.