XML External Entity is Ignored (Error Code 1001)

Problem

When the target of an XML external entity is on the local file system but not inside one of the framework folders or in the DITA-OT folder, Oxygen XML Web Author shows a validation warning: The external entity &name; is ignored. (error code: 1001) and does not resolve the entity.

Solution

To solve the problem one can do one of the following:

Move the external entity in one of the framework folders or in the DITA-OT folder.
Configure the additional.frameworks.directories option to include the folder where the target of the entity is located.
Set the ignore.extenal.entities.outside.frameworks option to the boolean value false.