There's always an ambiguity in metaphors comprising directions and the like: Is it the direction the user is wanting to take, or is the direction the user is wanting the object of his/her interaction to take? (Most of the time these will be opposite directions.)

Example: Scroll bars aren't as obvious as we may think and Apple has successfully changed their orientation. (In this case: Is it the direction the document should take inside the view or is it, where the user is wanting the viewport to go inside the document?)

We could refer to this as "object view" and "subject view" – and the ambiguity being, whether the interaction is bound to the object or to the subject.

Furthermore there's an ambiguity of time involved: Is it the direction, the elevator is going to take before I enter, or after I entered? (In terms of object vs subject: Am I calling the elevator or am I telling the mechanism where I would want to go?)