Data-flow diagram: Difference between revisions

Revision as of 06:14, 4 November 2005

Revision as of 06:16, 4 November 2005

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{{cleanup-date|February 2005}}

A '''data flow diagram''' ('''DFD''') is a graphical representation of the "flow" of data through an [[information system]]. A '''data flow diagram''' can also be used for the [[visualization]] of [[data processing]] (structured design). It illustrates the processes, data stores, and external entities in a business or other system and the data flows between these things. It is common practise for a designer to first draw a context-level DFD first which shows the interaction between the system and outside entities. This context-level DFD is then "exploded" to show more detail of the system being modelled.

In analysing a business, several sets of DFD's are drawn. Initial DFD's might model the existing system (flaws and all), while later DFD's may model a solution to the problem being analysed. For these solution DFD's a logical and physical DFD is drawn. Physical DFD's represent physical files and transactions, while logical or conceptual DFD's can be used to represent business functions or processes.

Data flow diagrams were invented by Larry Constantine, the original developer of structured design, based on Martin and Estrin's "data flow graph" model of computation.

==Types of DFD==

In analysing a business, several sets of DFD's are drawn. Initial DFD's might model the existing system (flaws and all), while later DFD's may model a solution to the problem being analysed. For these solution DFD's a logical and physical DFD is drawn. Physical DFD's represent physical files and transactions, while logical or conceptual DFD's can be used to represent business functions or processes.

==Components==

A data flow diagram illustrates the processes, data stores, and external entities in a business or other system and the data flows between these things. Four diagramatical components are used to develop a DFD. These are:

* Data Flow (represented by an arrow)

* Data Process (represented by a circle or rounded rectangle)