This paper explores the interpretation of specifications in the context of an object-oriented programming language with subclassing and method overrides. In particular, the paper considers annotations for describing what variables a method may change and the interpretation of these annotations. The paper shows that there is a problem to be solved in the specification of methods whose overrides may modify additional state introduced in subclasses. As a solution to this problem, the paper introduces data groups, which enable modular checking and rather naturally capture a programmer's design decisions.

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