description of a set of action sequences, including variants, that 
          a system performs that yields an oberservable result to a particular 
          actor.
        Example: 
        actors: customer, sales person, store keeper
        action sequence: Store Procurement
        
          
            - customer to sales person - request product
- sales person to store keeper - check status
- store keeper to sales person -deliver product
- sales person to customer - deliver product
 
        Use Case Scenario
        