On definability in the nondeterministic information system. (English) Zbl 0677.68110

Summary: We introduce several approximation operations \b{E}\({}_ i\) in the space (U,E), where E is a cover of a set U. In particular when E is a partition of U, they are reduced to the operations \b{X} and \(\bar X\) of Pawlak. We investigate the properties of the operations \b{E}\({}_ i\), the relations among them and their connections with set-theoretical oprations \(\cup\), -, \(\cap\). We examine the notions of definability with respect to the introduced operations. We apply the results obtained to the nondeterministic information systems, but the scope of applications may be extended.


68P20 Information storage and retrieval of data
93A99 General systems theory