Data-flow models are used to show how data flows through a sequence of processing steps. For example, a processing step could be to filter duplicate records in a customer database. The data is transformed at each step before moving on to the next stage. These processing steps or transformations represent software processes or functions when data-flow diagrams are used to document a software design. However, in an analysis model, people or computers may carry out the processing.
A data-flow model, which shows the steps involved in processing an order for goods (such as computer equipment) in an organisation, is illustrated in Figure 2. This particular model describes the data processing in the ‘Place equipment order’ activity in the overall process model shown in Figure 1. The model shows how the order for the goods moves from process to process. It also shows the data stores (Orders file and Budget file) that are involved in this process.