nduction can be characterized as a bottom-up method in defining some elements of a set. There is however an Top-down method, saying that the set is the smallest set
closed under the rules.
There monotone and non-monotone induction. So when we deal with more variables we should examine tow cases: monotone and non-monotone.
For more information about “inductive Definitions” see: P.Aczel, Inductive Definitions, Chapter 7, In J. Barwise handbook of Mathematical Logic