Data flow diagram

A data flow diagram and data flow diagram (English dataflow diagram ) represents the type of use, deployment, and modification of data within a program dar. It can also be used, the data flow of a process or activity to reproduce (eg the use of data and change in the quoting process in a commercial enterprise ). A data flow diagram has no control flow, there is no decision rules and no loops. The concrete operations on the data can be represented by a flow chart.

When data flow diagram four element types are distinguished with the following semantics:

  • Data memory: represented by two parallel lines, between which the memory name is ( modeled in UML as a buffer node).
  • Data Flow: represented by an arrow by name. The intervention of a function to read and write to a data memory can be represented either do this with two separate arrows or with a double arrow.
  • Function ( or process): represented by a circle with name (comparable to the activity in the UML).
  • Interface to the environment represented by a rectangle containing the interface name (external partners). Interfaces at which feed data into the system, data sources may be mentioned. Interfaces where disappearing data from the system are called data sinks.

There are different notation for the representation of data flow diagrams. The notation introduced above was described in 1979 by Tom DeMarco in the context of structured analysis. Previously the symbols from DIN 66001 were used. This notation is, however, rather uncommon today.

Each data flow at least one of the endpoints ( source and / or destination) must be a process. The refined representation of a process can be carried out in another data flow diagram that the process is divided in sub-processes.

The data flow diagram is the essential modeling tool for structured analysis.

When using the UML usually takes over the activity diagram, the role of the data flow diagram.

A special form of data flow plan is the set -oriented data flow diagram, also called Who / what - diagram. The activities will be assigned to each participant in vertical swimlanes per participant.

Furthermore, one can interpret data flow diagrams as inverted Petri nets, because courts in such networks correspond to the semantics of data stores. Similarly, the semantics of transitions from Petri nets and data flows and functions of data flow diagrams is to be regarded as equivalent.

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