PINGDOM_CANARY_STRING It's easy to understand the flow of data through systems with the right data flow diagram software. This guide provides everything you need to know about data flow diagrams, including definitions, history, and symbols and notations. You'll learn the different levels of a DFD, the difference between a logical and a physical DFD and tips for making a DFD. 7 minute read Want to make a DFD of your own? Try Lucidchart. It's quick, easy, and completely free. A data flow diagram (DFD) maps out the flow of information for any process or system. It uses defined symbols like rectangles, circles and arrows, plus short text labels, to show data inputs, outputs, storage points and the routes between each destination. Data flowcharts can range from simple, even hand-drawn process overviews, to in-depth, multi-level DFDs that dig progressively deeper into how the data is handled. They can be used to analyze an existing system or model a new one. Like all the best diagrams and charts, a DFD can often visually “say” things that would be hard to explain in words, and they work for both technical and nontechnical audiences, from developer to CEO. That’s why DFDs remain so popular after all these years. While they work well for data flow software and systems, they are less applicable nowadays to visualizing interactive, real-time or database-oriented software or systems. Data flow diagrams were popularized in the late 1970s, arising from the book Structured Design, by computing pioneers Ed Yourdon and Larry Constantine. They based it on the “data flow graph” computation models by David Martin and Gerald Estrin. The structured design concept took off in the software engineering field, and the DFD method took off with it. It became more popular in business circles, as it was applied to business analysis, than in academic circles. Also contributing were two related concepts:
Three other experts contributing to this rise in DFD methodology were Tom DeMarco, Chris Gane and Trish Sarson. They teamed up in different combinations to be the main definers of the symbols and notations used for a data flow diagram. Three common systems of symbols are named after their creators:
One main difference in their symbols is that Yourdon-Coad and Yourdon-DeMarco use circles for processes, while Gane and Sarson use rectangles with rounded corners, sometimes called lozenges. There are other symbol variations in use as well, so the important thing to keep in mind is to be clear and consistent in the shapes and notations you use to communicate and collaborate with others. Using any convention’s DFD rules or guidelines, the symbols depict the four components of data flow diagrams.
Want more detail? Here is a comprehensive look at diagram symbols and notations and how they’re used.
Diagramming is quick and easy with Lucidchart. Start a free trial today to start creating and collaborating. Make a DFDA data flow diagram can dive into progressively more detail by using levels and layers, zeroing in on a particular piece. DFD levels are numbered 0, 1 or 2, and occasionally go to even Level 3 or beyond. The necessary level of detail depends on the scope of what you are trying to accomplish.
Using DFD layers, the cascading levels can be nested directly in the diagram, providing a cleaner look with easy access to the deeper dive. By becoming sufficiently detailed in the DFD, developers and designers can use it to write pseudocode, which is a combination of English and the coding language. Pseudocode facilitates the development of the actual code. Data flow diagrams are well suited for analysis or modeling of various types of systems in different fields. DFD in software engineering: This is where data flow diagrams got their main start in the 1970s. DFDs can provide a focused approached to technical development, in which more research is done up front to get to coding. DFD in business analysis: Business analysts use DFDs to analyze existing systems and find inefficiencies. Diagramming the process can uncover steps that might otherwise be missed or not fully understood. DFD in business process re-engineering: DFDs can be used to model a better, more efficient flow of data through a business process. BPR was pioneered in the 1990s to help organizations cut operational costs, improve customer service and better compete in the market. DFD in agile development: DFDs can be used to visualize and understand business and technical requirements and plan the next steps. They can be a simple yet powerful tool for communication and collaboration to focus rapid development. DFD in system structures: Any system or process can be analyzed in progressive detail to improve it, on both a technical and non-technical basis. While a DFD illustrates how data flows through a system, UML is a modeling language used in Object Oriented Software Design to provide a more detailed view. A DFD may still provide a good starting point, but when actually developing the system, developers may turn to UML diagrams such as class diagrams and structure diagrams to achieve the required specificity. These are the two categories of a data flow diagram. A Logical DFD visualizes the data flow that is essential for a business to operate. It focuses on the business and the information needed, not on how the system works or is proposed to work. However, a Physical DFD shows how the system is actually implemented now, or how it will be. For example, in a Logical DFD, the processes would be business activities, while in a Physical DFD, the processes would be programs and manual procedures. Want to know more? See our deeper look into Logical DFDs vs. Physical DFDs. You can create your own DFD online with Lucidchart. Use our DFD examples and specialized notations to visually represent the flow of data through your system. Our data flow diagram maker is simple, yet powerful. Get started with a template, and then use our shapes to customize your processes, data stores, data flows and external entities. Data flow diagramming is quick and easy with Lucidchart. Start a free trial today to start creating and collaborating. Want to make a DFD of your own? Try Lucidchart. It's quick, easy, and completely free. |