[Excerpt] Labour scheduling is an important function performed by managers of service operations. Customers demand rapid response times, requiring that appropriate numbers of employees are present at all times. Having too many staff on hand lowers operating margins, while having too few servers risks the loss of present or future business. The task of balancing labour capacity and demand – labour scheduling – is made more difficult by demand that often varies widely during the operating day, since the customer-contact activities performed by service delivery personnel cannot be inventoried. Further increasing the difficulty of developing labour schedules is the fact that managers often resort to using employees available for work only during individually specified portions of the operating day (a condition we call limited time-availability). This occurs when labour supplies are tight or when managers desire (or require) the scheduling flexibility offered by employees willing to work part-time.