Data Flow Diagrams
Concept of Data Flow Diagrams (abbreviated as DFDs) was introduced by De-Marco in 1978 and also by Gane and Sarnon in 1979. DFD is an important tool used by system analyst. In simple, DFD gives an outline modeling of the system to be built and also can be designed to study the data flow of already existing system in a graphical interface.
As an Architect who draws sketches of the house that is to be built, he does it after gathering the requirements of house buyer and then translates it into a blueprint that gathers all engineering requirement for the house. Misinterpretation may take place when an architect talks to the house buyer about the model of house with his words, surely house buyer won’t understand all his ideas. Once a wise man said that people understand 100% of what they see but only 50% of what they listen. So, to describe his model to house buyer architect can use drawings and models.
In a similar way, a system analyst compared to an architect and user to house buyer. A meeting between these two parties to get an output of usually two types; a business requirement outline and prototype of the way the system will function, and a schematic represented by modeling tools for programmers. This meeting can be taken as the requirement gathering session of System Development Life Cycle (SDLC).
Figure 1 – The interfaces required to design and build a house
Figure 2 – The interfaces required to design and build a system
So, a DFD models a system by using external entities from which data flows to a process which transforms the data and creates output data flows which go to other processes or external entities or data stored. Similarly, stored data may also flow to processes as inputs. DFD is perfect and simple way of modeling a system for ease of understanding and at the same time is very flexible too. Designing of DFD is easy and simple because it uses only four symbols. Least number of symbols used in DFD makes it look neat and is easy to understand.