olemus
süsteemi arhitektuuris: kogum loogikafunktsioone,
mis hõlmavad üht või mitut infoobjekti ning
on ettemääratud tingimustel alati tõesed

ISO/IEC/IEEE 24765:
set of predicates on one or more information objects which must always be true
Note 1.The predicates constrain the possible states and state changes of the objects to which they apply. Thus, an invariant schema is the specification of the types of one or more information objects that will always be satisfied by whatever behavior the objects might exhibit.