A flow conveys data between processes, external entities, and data stores. It represents data in motion, which can be computerized components, such as messages or bits, or non-computerized components, such as eggs or cake for example.
A flow cannot link two data stores or two external entities without going through a process or a split/merge.
Flows outgoing from data stores are interpreted as a read access to information in the data store.
Flows incoming to data stores are interpreted as a write, update, or delete access to information in the data store.
You design a DFD flow using a BPM flow (or a resource flow object when the destination object is a data store) with a Flow stereotype. Flows incoming to and outgoing from data stores must be created with the Resource Flow tool when using the DFD specific toolbox.
The Data tab in the property sheet displays the data transported by the flows.