Is it possible to create a three-way many-to-many relationship?  If so, how would you tackle this?  
I'm thinking of employees, positions (or billets), and position titles.  Some employees over time move to and hold new positions, but you don't want to delete the person's historical records. Thus, in your database one employee may hold multiple positions over time.  
Also, you often have situations where the new incoming employee holds the same position as the outgoing employee, overlapping for a time during a handover period, meaning you technically have two persons in the same position at the same time.  
Lastly, position titles are often shared across positions and employees.  
I see multiple relationships in three directions here.  How can you set this up?
--Kent J.