Data flow diagrams

Data flow diagrams
See also
Knowledge map Algorithm Information theory Parametric analysis Decision tree Decision table Knowledge tree Documented procedure Learning map

Data flow diagrams are a tool for the description, analysis and design of information systems, whose origins date back to the first generation of information systems (transactional systems, batch systems).

In a graphic way, they present the basic relationships occurring in information processes, the advantage of which is the maximum simplification of the symbolism used. There are only 4 symbols, meaning: process, data warehouse, flow, terminator. The symbolism proposed by Youdon-DeMarco is presented in the figure below.

Data flow diagram.gif Fig. Symbolism used in data flow diagrams

Preparation rules

Using the data flow diagrams, there are a few rules to keep in mind:

• there are no procedures (processes) of beginning and end,
• there are no loops or decision blocks,
• you should use unique names of processes and flows (it is useful to number them),
• naming flows to and from the data store is not suitable
• flow between data stores and between terminators is unacceptable,
• the data warehouse should be used for at least two processes,
• an arrow towards the data warehouse means that specific changes are made (introduction, update, deletion),
• an arrow from the data store means that the data is read,
• the diagram can describe automated and manual flows,
• the diagram can be created at various levels of detail.

References

• Batini, C., Nardelli, E., & Tamassia, R. (1986). A layout algorithm for data flow diagrams. IEEE Transactions on Software Engineering, (4), 538-546.
• Bruza, P. D., & Van der Weide, T. (1989). The semantics of data flow diagrams. University of Nijmegen, Department of Informatics, Faculty of Mathematics and Informatics.
• Tse, T. H., & Pong, L. (1989). Towards a formal foundation for DeMarco data flow diagrams. The Computer Journal, 32(1), 1-12.