In the rehabilitation management domain, we find many situations where actors have to manage complex cases. To facilitate patients' quick recovery from their individual conditions, case managers need a high degree of flexibility in organizing their tasks. Unfortunately, giving them complete flexibility is challenging for two reasons: Firstly, process owners may want to tame the flexibility to conform with compliance policies. Secondly, without complete information about the possible processes in the problem domain, software engineers are struggling to design information systems that can support these case management processes effectively. In this paper, we will therefore show how semantic web technologies can complement adaptive case management techniques in order to cope with the cases' flexibility. Following the ideas of linked data and the open-world assumption, these techniques facilitate (1) a data structure that is easily extendable, (2) data quality improvements, and (3) the definition and checking of business rules using domain concepts. As a proof of concept, we integrated the method into a case management tool and conducted a small case study using real-life examples from the rehabilitation domain.