Assignment problems involve optimally matching
the elements of two or more sets, where the
dimension of the problem refers to the number
of sets of elements to be matched. When there
are only two sets, as will be the case for most of
the variations we will consider, they may be
referred to as ‘‘tasks’’ and ‘‘agents’’. Thus, for
example, ‘‘tasks’’ may be jobs to be done and
‘‘agents’’ the people or machines that can do them.
In its original version, the assignment problem
involved assigning each task to a different agent,
with each agent being assigned at most one task
(a one-to-one assignment). While only two of the
models to be discussed involve assigning multiple
agents to a task , some of the models do
assign multiple tasks to the same agent (a one-tomany
assignment). The models to be discussed
first, however, assign no more than one task to
any given agent.