Process support systems, such as workflows, are being used in a variety of domains. However, most areas of application have focused on traditional production-style processes, which are characterised by predictability and repetitiveness. Application in non-traditional domains with highly flexible process is still largely unexplored. Such flexible processes are characterised by lack of ability to completely predefine and/or an explosive number of alternatives. Accordingly we define flexibility as the ability of the process to execute on the basis of a partially defined model where the full specification is made at runtime and may be unique to each instance. In this paper, we will present an approach to building workflow models for such processes. We will present our approach in the context of a non-traditional domain for workflow, deployment, which is, degree programs in tertiary institutes. The primary motivation behind our approach is to provide the ability to model flexible processes without introducing non-standard modelling constructs. This ensures that the correctness and verification of the language is preserved. We propose to build workflow schemas from a standard set of modelling constructs and given process constraints. We identify the fundamental requirements for constraint specification and classify them into selection, termination and build constraints. We will detail the specification of these constraints in a relational model. Finally, we will demonstrate the dynamic building of instance specific workflow models on the basis of these constraints.