he attributed diagraph is presented to specify the structure and properties of data flow diagrams (DFD), and a binary relation called the edge (flow) composition relation is proposed as the base on which the notion of balance between a DFD and its child DFD is formally defined. By using the above-mentioned approach, this paper provides a formal specification of DFD which is stronger than those found in the literature. Moreover, this approach applies to different sorts of DFD, including DeMarco DFD, DFD for real-time systems and so on.