Approximations in hyperrings.

*(English)*Zbl 1236.16044Summary: This paper considers a relationship between rough sets and hyperrings. It is devoted to approximation operators within approximation spaces based on Krasner hyperrings. These approximation spaces consist of universes of hyperrings and various equivalence relations on these universes. It investigates approximation operators determined by equivalence relations defined by means of normal hyperideals of hyperrings. It considers also approximation spaces connected with strong homomorphisms between hyperrings where equivalence relations are defined by homomorphisms kernels, homomorphism images and counter images of hyperideals by which, in most cases, they are also hyperideals.