Data flow diagrams are essential in developing information systems as they are used to graphically represent the flow of data within an information system. DFD is a form of process modelling and is made up of four components; processes, external entities, data flows and data stores.
Processes refer to jobs that are done with the data, and transforming incoming data flows to outgoing flows. External entities refer to any class of people, an organization, or another system which exists outside the system that interacts with the system. These are the places which provide the organisation with data, or have data sent to them by the organisation (e.g. customers, partners, government bodies). Data flows then mark movements of data through the system and connects the processes, external entities and data stores. Finally, data stores are data at rest. They represent holding areas for collection of data, processes add or retrieve data from these stores. Processes are the only component that connect to data stores.
There are many reasons why DFD’s are used in developing information systems.Firstly, they provide a pictorial and non-technical representation. They are also easy to understand and amend and quick to produce. Furthermore, they use a limited number of symbols with specific meaning which leads to concise system descriptions. Basically, the reason we do process modelling is to improve the operation of a system, not just to change its physical form.
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