An incremental updating principle for computing approximations in information systems while the object set varies with time

Approximations of a concept in the variable precision rough set model will change when an information system varies with time. Usually, it is an effective method to carry out incremental updating approximations by using existing information in the dynamic environment. This paper focuses on the incremental updating principle of computing approximations while objects in information systems dynamically change. The properties of approximations and approaches for updating approximations are provided while objects in the universe evolve over time.