System State

Collection of variables necessary to fully describe the system at a point in time

• Number-in-queue
• Number-of-servers
• Status-of-servers

Event Notice

• Instantaneous occurrence that changes the state of system
  • Arrival of customer
  • Completion of service
  • Breakdown of machine

Activity

• Duration of time of specified length known when begins; scheduled & desired;
  • Unconditional wait
• Duration determination
  • Deterministic: always 10 minutes
  • Statistical: Uniform (1,10)
  • Functional: based on attribute (age, capacity)
• Begins & Ends with an Event Service time: Begin Service, End Service

Event List

• Collection of associated entities, ordered in some manner
  • FIFO queue of customers
  • Priority queue of customers
  • Available servers

Delay

• Duration of time of unspecified, indefinite length not known until it ends; duration determined by system conditions; i.e. by other events or activities; not scheduled or desired
  • Conditional wait
  • Time waiting in queue
  • Time waiting on any other event

Clock

• Variable representing simulated time
  • Elapsed time in smallest time unit necessary
• Updated with each new event time as the event is executed