Approach Data Flow Diagrams

Structured approach in the development of information systems describing activities, which occur in business processes, as processes that must be carried out by people or computers. Graphic modeling are believed to be useful for process modeling (modeling processes) is a data flow diagram (DFD)

DFD is a graphical modeling system that represents the system requirements as processes, external agents, the data flows, and data stores. Here is an explanation of the notation used in the DFD:

1. External agent, a person or organization outside the scope of systems that provide input data or receive data output. External agents can act as a sink (receiver of data) only, source (donor or data source), or as both.
2. Process, represents an algorithm or procedure that processes or transform input data into output data.
3. Data flow, an arrow on the DFD that represent the flow of data movement from or heading to the processes, the data stores, and external agents.
4. Data store, is where data is stored for future access needs by one or more processes.

If you see, a process that is in the DFD can be adapted from a use case that is in the event table. In addition, source, trigger, response, and destination in the event table is represented in the DFD through external agents and data flow. Therefore, DFD also describe the system use cases that respond to every event that happens in a business process. Furthermore, each data store in DFD can also be adapted from the entity relationship diagram (ERD) that have been made previously. Therefore, DFD also integrates processes that are triggered by events in the data entities that have previously modeled by using the ERD.

The greater the scope of the system are discussed, the more complex the resulting DFD. In order to provide detailed modeling, it is not uncommon enactment level of abstraction at the time of depiction DFD. Level of abstraction is a modeling technique that breaks down into a series of hierarchical system used to describe the model in more detail. There are many types of DFD that can be used to describe the system requirements, such as

1. Context diagram. the DFD that summarizes the overall activity of the processes that occur in the system, with only using a notation process. Context diagram clearly will represent the scope of the system. Context diagram does not show the data stores because the data store is used in the system is allegedly contained in the scope of the system. Meanwhile, external agents are outside of the scope of the system. However, the data stores can only appear on the context diagram that models the new system, which is where the system also interacts with other systems

2. DFD fragment, the DFD that describes only a process of response to an event. DFD fragment was made for each use case that is triggered by an event in the event table. Each DFD fragment is a single modeling of a process system that responds to an event. System analysts usually make DFD fragments one-by-one, in order to better focus to produce the correct modeling of parts of the system to be built

3. Event-partitioned system models or diagrams 0, the DFD modeling system requirements by using a single process for each event in the system or subsystem. To create a diagram 0, each DFD fragments combined into a DFD. Diagram 0 is used as the main presentation tool. 0 diagram summarizes the overall system or subsystem in a more detailed level when compared with a context diagram

4. Diagram 1, the DFD is used to further specify again the process that is in Diagram 0. Note that not all processes in the diagram 0 can be decomposed again into a diagram 1. Diagram 1 is often referred to as a detailed diagram.

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