This paper presents CDDF, a model of computation underpinning the formal semantics of a number of parallel programming languages. CDDF integrates control flow elements for the dynamic construction of task graphs, and data flow elements to express dependent computations and to decouple these using unbounded streams (Kahn process networks). It is a common ground to define the formal semantics of imperative programming languages with dynamic task creation, as well as data-flow or concurrent functional languages, as a special case of more general dependent task languages with channels or streams. We prove essential properties for languages fitting this model of computation, including deadlock-freedom, functional and deadlock determinism, and serializability. We also compare the model's hypotheses with Cilk's strictness and the Kahn principle.
