Data flow diagram
A data flow diagram or data flow diagram ( engl. Dataflow diagram ), the method of use, the provision and modification of data within a program . It can also be used to control the data flow of a process or activity play (z. B. the data using and change in the preparation of offers in a trading company). A data flow diagram has no control flow , there are no decision rules and no loops . The specific operations on the data can be represented by a program flow chart.
A distinction is made between four element types with the following semantics in the data flow diagram :
- Data storage : represented by two parallel lines with the storage name between them (can be modeledas a buffer node in the UML ).
- Data flow : represented by an arrow with a name. If a function has read and write access to a data memory, this can be shown either with two separate arrows or with a double arrow.
- Function (or process ) : represented by a circle with a name (comparable to the activity in UML ).
- Interface to the environment : represented by a rectangle that contains the interface name (external partner). Interfaces at which data flow into the system are called data sources. Interfaces at which data flows out of the system are called data sinks.
There are different notations for representing data flow diagrams. The notation presented above was described by Tom DeMarco in 1979 as part of the structured analysis .
For every data flow, at least one of the endpoints (source and / or destination) must be a process. The refined representation of a process can take place in a further data flow diagram that divides this process into sub-processes.
The data flow diagram is one of the modeling instruments of structured analysis . When using the UML , the activity diagram usually takes on the role of the data flow diagram. A special form of the data flow plan is the job-oriented data flow plan, also known as the "who / what diagram". The activities are assigned to the individual participants in vertical swim lanes per participant.
Furthermore, data flow diagrams can be understood as inverted Petri nets , because places in such nets correspond to the semantics of data memories . Analogous to this, the semantics of transitions from Petri nets and data flows and functions from data flow diagrams are to be regarded as equivalent.
literature
- G. Schmidt: Method and techniques of organization. 13th edition. Giessen 2003, ISBN 3-921313-62-7 .
- P. Stahlknecht, U. Hasenkamp: Introduction to business informatics. 11th edition. Berlin 2005, ISBN 3-540-01183-8 .
Web links
- yEd Graph Editor - free diagram editor that can be used to draw data flow diagrams
- Orinoco - free tool for modeling and simulating data flow diagrams