V is a ``wide-spectrum'' language: it includes sets, mappings, relations, predicates, enumerations, state transformation sequences, and both declarative and procedural statements.
A high-level program in V is refined into executable code by applying transformation rules.
Optimization: e.g., move a predicate outside a quantifier. For example, if p does not depend on x , &forall x [ p &and q &rArr r ] &rarr p &rArr &forall x [ q &rArr r ]
Cf. moving invariant computations out of loops.
Refinement: move code closer to executable form, e.g., convert a bounded quantifier into a loop, or implement a set by means of a data structure.