%A Mar Yah Said %A Michael Butler %A Colin Snook %T Class and State Machine Refinement in UML-B %X UML-B is a ?UML-like? graphical front end for Event-B. It adds support for object oriented modeling concepts while visually retaining the Event-B modeling concepts. In the continuity of the work on UML-B, we strengthen its re?nement concepts. Development in Event-B is done through re?nements of an abstract model. Since Event-B is re?ected in UML-B, the abstraction-re?nement concepts must also be catered for in UML-B. UML-B introduced the new concept of re?nement, where model complexity is managed by introducing more detailed versions of a machine. We extend this re?nement concept by introducing the notion of re?ned classes and re?ned state machines. A re?ned class is one that re?nes a more abstract class and a re?ned state machine is one that re?nes a more abstract state machine. The UML-B drawing tool and Event-B translator are extended to support the re?nement concepts. A case study of an auto teller machine (ATM) is presented to demonstrate the notion of re?ned classes and re?ned state machines. %D 2009 %L deploy433