It is very often more convenient and more meaningful to specify a set of structural descriptions analytically rather than generatively, i.e., by specifying a set of constraints each structured description in the set has to satisfy. Peters and Ritchie [7] have shown that if context-sensitive rules are used only for “analysis” then the string language of the set of trees is still context-free. In this paper, we have generalized this result by considering context-free rules constrained by Boolean combinations of proper analysis predicates and domination predicates. These rules, called "local transformations" not only make precise an informal and briefly discussed notion of Chomsky [2], but also, generalize it in an appropriate manner. It is shown that the Peters-Ritchie result can be generalized to local transformations. Linguistic relevance of this result has been also briefly discussed. Results in this paper are relevant to the following situation: Patterns of a class, say A, may be difficult to characteri...