If you delete an existing element/method in a schema/class file, and reload the schema/class file, stale aliases are generated. You can delete these stale aliases from the rules composer DC, provided they are not being used in the rule.
In the Project Explorer view, double click the Aliases node.
In the Project Aliases Editor, choose the XSD Aliases/Class Aliases tab and choose the Stale Aliases as shown below:
Choose Delete Aliases button.