What is the official Oracle Primavera's definition of an External Link?

Hi,

This must be an easy question for an Oracle person.

There is a recent debate among our schedulers about the term external link. One group said, "it is an activity relationship link from the current project from/to an activity of a project outside the current project's scheduling database". As such, it is a link from the current project to an external project, usually a contractor project residing in the contractor's database. It does not matter whether the external project is open or close. Has anyone done this before? How do you go about progressing?

Another group said, "it is an activity relationship link from open project from/to an activity of any closed project." This one includes link to close projects within the same database..