Adaptive Case Management (ACM) has emerged as a key BPM technology for supporting the unstructured business process. A key problem in ACM is that case schemas need to be changed to best fit the case at hand. Such changes are ad hoc, and may result in schemas that do not reflect the intended logic or properties. This article presents a formal approach for reasoning about which properties of a case schema are preserved after a modification, and describes change operations that are guaranteed to preserve certain properties. The approach supports reasoning about rollbacks. The Case Management model used here is a variant of the Guard-Stage-Milestone model for declarative business artifacts. A real-life example illustrates applicability.