In queuing theory with multiple servers, the nature of the waiting situation can be studied and analysed mathematically, if
1. the complete details of the items in the waiting lines are known
2. the arrival and waiting times are known and can be grouped to form an appropriate waiting line model
3. all the variables and constants are known, and they may form a linear equation
4. the laws governing arrivals, service times and the order in which the arriving units are taken into service are all known