Redefining terms related to dependability

Dependability is an integrative concept that encompasses the following attributes: availability (readiness for correct service), reliability (continuity of correct service) and safety (absence of catastrophic consequences for the user(s) and the environment). In this paper we redefine these attributes. We are looking at them not only as concepts but as quantities. That makes it possible to measure or estimate them by experiments. The measurability makes the quantities more comprehensive and allows defining experiments to get values and to compare different solutions with each other.