  In workflows and business processes, there are often security requirements on
both the data, i.e. confidentiality and integrity, and the process, e.g.
separation of duty. Graphical notations exist for specifying both workflows and
associated security requirements. We present an approach for formally verifying
that a workflow satisfies such security requirements. For this purpose, we
define the semantics of a workflow as a state-event system and formalise
security properties in a trace-based way, i.e. on an abstract level without
depending on details of enforcement mechanisms such as Role-Based Access
Control (RBAC). This formal model then allows us to build upon well-known
verification techniques for information flow control. We describe how a
compositional verification methodology for possibilistic information flow can
be adapted to verify that a specification of a distributed workflow management
system satisfies security requirements on both data and processes.
