In this paper, we investigate the properties of rough approximations defined by preordered sets. We study the relations among the lower and upper rough approximations, closure and interior systems, and closure and interior operators.

Acyclic phase-type distributions form a versatile model, serving as approximations to many probability distributions in various circumstances. They exhibit special properties and characteristics that usually make their applications attractive. Compared to acyclic continuous phase-type (ACPH) distributions, acyclic discrete phase-type (ADPH) distributions and their subclasses (ADPH family) have ...

Information flow considers whether a High-level user in a multi-level system can pass information to a Low-level user. Many information flow properties suffer from the so called refinement paradox ; i.e. a property holds for a process but does not hold in one of its refinements. Therefore, it is often desirable to consider the refinement closure of an information flow property. The refinement c...