Change the declaration of an entity
Change the declaration of an internal entity
You can change the name of a declared internal entity (but not its content).
Change the declaration of an external entity
You can change the name of a declared external entity and/or the name of the file (but not its content).
Remove the declaration of an entity
Remove the declaration of an internal entity
You can remove the declaration of an internal entity if there are no references to this entity.
Remove the declaration of an external entity
You can remove the declaration of an external entity if there are no references to this entity in the document.