On User Supplied Evaluations of Time-Shared Computer Systems

Comments are made regarding the collection of user preference data for varying characteristics of time-sharing systems. These ``utility functions,´´ when determined for a number of variables, can be used as an aid to managers and designers of time-sharing service facilities. There are, however, several practical problems in assessing utility functions of more than one variable. These stem mainly from the fact that utility functions of several variables are generally not simple additive functions of utilities for single variables. In most cases they are complex functions consisting of many more component utility functions than the number of variables. This difficulty stems from the fact that preferences for a set of variables describing a service facility (such as a time-sharing system) are generally not independent of current values of other variables. This is known as ``utility dependence.´´ If, however, a sufficient number of ``utility independence´´ relationships can be found (by interview procedures) then it is possible to assess multidimensional utility functions with a more practical effort. Procedures for this assessment and uses of utility functions in managing a time-sharing system are described here.