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A data flow diagram (DFD) is type of flowchart, a graphical representation of the flow of data through an information system. It is also known as a data flow diagram, function diagram, or process diagram. Data flow diagrams are used to design the architecture of an information system and to document the functional aspects of it.
Data Flow Diagram
A data flow diagram (or DFD) is a graphical representation of the information flow in a business process. It demonstrates how data is transferred from the input to the file storage and reports generation.
By visualizing the system flow, the flow charts will give users helpful insights into the process and open up ways to define and improve their business.
DFD was highlighted in the book “Structured Design” by Ed Yourdon and Larry Constantine in the 1970s. With the success of the structures design concept in the software engineering field, people began to acknowledge DFD as a useful tool. From there, its scope of usage expanded, especially in business circles.
There are other people who contributed to developing this method, such as Tom DeMarco, Chris Gane, and Trish Sarson. They came up with the symbols and notations used in process flow diagrams.
An external entity, also known as terminators, sources, sinks, or actors, is an outside process where information enters or leaves the system. It acts as the source and the destination of the information.
Thus, it is usually placed at the edge of the diagram. External entities can either be a person, an organization, or a computer system.
Unlike other flowchart symbols, which are triangles, rectangles, or circles, a DFD uses stick-figure drawings to demonstrate external entities.
The process is a procedure that makes changes to the information and its flow, resulting in new output. A process can perform several functions, from carrying out computations, categorizing information based on logic, or using business rules to change the flow.
It is labeled with a short and simple term that describes the whole process, such as “Submit payment”.
Data store is a place that contains information for later use. It can be files, documents, or a filing cabinet. A data store stays between two processes, receiving and sending the inputs and outputs. In business process diagrams, this component is in the form of two horizontal lines.
Data flow is the direction that the information takes to pass from external entities to processes and stores. A DFD shows this route by using arrows and succinct labels. Users will get the interface among the three components above by observing the system’s information path.
Levels In A DFD
A DFD can be divided into levels and layers, starting with level 0; thus, users can focus on describing a particular stage.
This level, known as the Context Level, zeroes in on the whole system and its connection to the external entities. Users can digest the system as a high-level process with a broad overview when using a level 0 DFD. It is designed to be straightforward so that a wide range of audiences can easily digest it.
Level 1 DFD is a more detailed level than the first one. It still describes the whole system but with emphasis on its main function and more sub-processes for easy digestion.
The next level goes deeper into parts of the previous one by dividing them into smaller sub-processes, requiring more text to narrate the details thoroughly.
Level 3 And Beyond
Level 3 and beyond are possible to make. However, diving in too deep into the small details can complicate the tool, hindering communications and efficiency.
Advantages Of A DFD
Data flow diagrams (DFDs) are a type of diagramming technique used in systems analysis and data modeling to represent system tasks and how they interact with each other. This can be seen as a notation for process flow charts. It provides instructions on how to process data. Data flow diagrams can help identify where problems in the system may be, allowing for the system to be repaired or redesigned before it falls apart. DFDs are also useful for teaching about the basics of computer science because it demonstrates how computers work by way of manipulating information, which is basically what all computers do.
Data flow diagrams provide a way for people who are involved in the process (such as managers and engineers) to better understand how objects are used in the system. It enables them to see how data is transferred from one object to the next, making it easier to spot errors. Data Flow Diagrams also offer a more natural and intuitive way for people unfamiliar with computers or programming languages to understand what's happening in the system.
When Can You Use A DFD?
A data flow diagram is a useful and flexible tool that can be helpful in different contexts.
In business, DFDs can be used to analyze since it breaks down the system and exposes flaws and bottlenecks. Plus, the tool’s graphic and simple representation gives the audience a deeper level of understanding.
Aside from business analysis, this method is also beneficial in re-engineering processes. This is a result of the former appliance. When users learn from the discovered inefficiencies, they can build a better data flow for their business.
In Software Engineering
Before developers get to the coding step, they have to carry out research on technical development. A data flow diagram is a great tool to do pre-code planning.
In System Structures
As mentioned above, DFDs reveal ways to improve a plan by uncovering its flaws. That is useful not only in business but also in many other fields. Whether technical or non-technical, you can use this tool to analyze and perfect your system structures.
How To Make A Data Flow Diagram?
Rules To Make A DFD
Before getting to the steps, let’s go through some rules on making one first.
- Each process needs to have a minimum of one input and one output.
- Since the data store receives and sends information, there should be data going in and out of it.
- The system’s information has to transform to produce output, so it needs to go through a process.
- Any process in this diagram must go to another process or a data store.
Choose The Process
Since different processes use DFD on different levels, selecting the process is important. Although a whole system can be put in a DFD, remember that larger processes come with difficulties to contextualize them. Hence, you should find out the piece you want to perfect and focus on it.
Sort Out The Business Activities
All of the activities in the process need to be categorized into four components: external entity, process, data flow, and data store.
Draw The Diagram
After the information is neatly grouped, you can start drawing your DFD. There are two ways to do this: by hand or using a diagram template and software.
Checking is always necessary to ensure your work is qualified. You should look for missed steps, redundant details, or unnecessary complexity in this step.
Creating Child Diagrams And Expanding
Once you have done the first diagram (the level 0 one), you can start working on the child diagram. Later, they will act as connectors between processes.
If you want to go deeper into analyzing the process, use level 1 and beyond diagrams to achieve the desired thoroughness.