arXiv subjects
Publications and source records attributed to Ewa Graczynska.
The aim of the paper is to present a solution of the problem 32 posed by K. Denecke, S.L. Wismath in: {\it Hyperidentities and clones}, Logic and Applications Vol. 14, Gordon and Breach Science Publishers, 2000.
We invent the notion of a derived and fluid variety. Fluid variety has no proper derived variety as its subvariety. We examine some properties of fluid and derived varieties. Examples of such varieties of bands are presented.
In the paper we consider the notion of hyper-quasi-identities and hyperquasivarieties as a generalization of the concept of quasi-identity and quasivariety invented by A. I. Mal'cev.