Directed relationships

[jdvorak001]

We do have a need for relationships that are only navigable in one direction. For instance, a Textual Document wants to specify the access rights by pointing at the apropriate Textual Document Accessibility Rights. There is however no way for the accessibility specification to know all the documents that reference it.

The way to express this is probably just to leave out the slash and the inverse link:

has-accessibility-rights : The Textual Document Accessibility Rights of the document.

Directed associations are the way to represent this in UML.

This was first brought up in #28.