  This paper deals with rate distortion or source coding with fidelity
criterion, in measure spaces, for a class of source distributions. The class of
source distributions is described by a relative entropy constraint set between
the true and a nominal distribution. The rate distortion problem for the class
is thus formulated and solved using minimax strategies, which result in robust
source coding with fidelity criterion. It is shown that minimax and maxmin
strategies can be computed explicitly, and they are generalizations of the
classical solution. Finally, for discrete memoryless uncertain sources, the
rate distortion theorem is stated for the class omitting the derivations while
the converse is derived.
