When we model, we create a number of views of the system being described - usually 2 or 3. For a complete description 3 are normally needed. Each view is an 'orthogonal' view. Each view is needed for a full understanding of the system. Views are orthogonal when:

	Each view has information that is unique to that view
	Each view has information that appears in other views
	The information that is common between views is consistent. (In this case it isn't. Can you spot the problem?)