A formal basis for some dependability notions Cliff B Jones School of Computing Science, University of Newcastle NE1 7RU, UK e-mail: cliff.jones@ncl.ac.uk Abstract. This paper shows how formal methods ideas can be used to clarify basic notions used in the field of dependability. Central to this endeavour is fixing a notion of system. Relationships between systems are also considered: in particular, the importance of the situation where one system is generated by another (possibly human) system is explored. The formalisation is used as a basis for definitions of the notions of fault, error and failure. Some applications to examples from the dependability literature and extensions of the basic model of system are also sketched. Please cite the original publication A Formal Basis for some Dependability No- tions, Cliff B Jones, in Formal Methods at the Crossroads: from Panacea to Foun- dational Support (eds.) Bernhard K. Aichernig and Tom Maibaum, Springer- Verlag, Lecture Notes in Computer Science, Vol. 2725, 2003