simple. When there are points on the moduli space with extra massless particles the situation is more involved. Then the moduli space ${\CM}_0$ is constrained also by the equations of motion of these particles. As one adds sources to the theory proportional to $F$-components of chiral operators, the expectation values of the chiral fields can move away from ${\CM}_0$. The simplest way to describe the situation in such a case is to use an enlarged field space $\CM$ which includes all the fields (including those massive fields which become massless at special points) and to write a superpotential on $\CM$. Then, the equations of motion derived from the superpotential lead to relations in the ring. These relations depend on the parameters in the theory – the sources.

In previously studied examples the structure of the chiral ring was relatively simple. In particular it was determined to a large extent by the symmetries. In general, the structure of the chiral ring can be quite involved. One may describe the ring in terms of generators satisfying certain relations. The relations in the classical chiral ring are consequences of the composite nature of the gauge invariant chiral operators . Quantum mechanically these relations 