We present a sufficient condition for a class C of effective interpret
ations in order that C has a uniform procedure enumerating (when first
-order oracle and recursive presentation of the interpretation involve
d are given) dynamic theories of interpretations in C. Under some addi
tional assumption on the enumerating procedure, this condition is nece
ssary. The main result states that if arithmetical notions are first-o
rder-definable by universal or existential formulas within interpretat
ions in C then C has an appropriate uniform procedure.