With the ever increasing popularity of mobile devices and the widespread deployment of different types of networks, pervasive environments have truly arrived. Although such environments are already being utilised to provide services based on the available data, the modelled domain knowledge is generally not formally verified for consistency and applicability within and across domains. This paper presents our knowledge-based verification and control approach and shows its need and effectiveness. In our system model, policies in the form of rules are authored at different levels of abstraction at different layers in the policy hierarchy. Top level rules are written in first-order predicate logic based on a formal ontology of the domain. Detection and resolution of feature interactions (or conflicts) is an important task in the policy hierarchy. Our running example is the pervasive mobile learning environment of a university campus. Our approach is easily and equally applicable to other pervasive environments.