In this paper, an approach to the modelling and implementation of data-flow diagrams (DFDs) using Petri nets is introduced. A direction is identified where visualisation and high-level semantics can be incorporated into data-flow diagrams to facilitate direct manipulation, interpretation and validation. At the automation level, visualised DFDs generate layouts for data-flow vectors and use Petri nets to safeguard the correctness of a specification. The Petri net model uses a set of constraints to enforce consistency, both within and across diagrams. At the visual level, visualised DFDs replace the traditional textual specifications of the process and data-flow components with graphical forms. The entity-relationship model is adopted as the hierarchical and logical view of data.