Data Flow Diagram with Examples - Video Rental System Example

Oct 25, 2026

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Tutorial introducing a Data Flow Diagram using a “Video Rental Store” as the example system. It explains how a context DFD contains one process and external entities (Customer and Manager), and how a level 1 DFD decomposes the system with multiple processes, data stores (Video Library, Rental), and data flows producing bills and receipts. It also provides DFD tips on appropriate level of detail and cautions against confusing data flow diagrams with process flow or activity flow.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages3

Reading Time8 min

AccessFree to download

Context DFD

Level 1 DFD

Data Flow Diagram Tips and Cautions

Be Aware of the Level of Detail

Don't Mix Up Data Flow and Process Flow

Visual Paradigm Data Flow Diagram with Examples-Video Rental System Example Tutorial Data Flow Diagram with Examples-Video Rental System Example Written Date : February 16, 2015 The Video Rental System Example Context DFD The figure below shows a context Data Flow Diagram that has been drawn for a video rental system. It contains a process (shape) that represents the system to be modeled, in this case, the " Video Rental Store." It also shows the participants who will interact with the system, called external entities. In this example, there are two external entities, namely Customer and Manager. In between the process and the external entities, there are data flow connectors that indicate the existence of information exchange between the customer and the system. A Context DFD is the entrance to a data flow model. It contains one and only one process and does not show any data stores, which makes the diagram simple. Level 1 DFD The figure below shows the level 1 DFD, which is the decomposition (i.e. , breakdown) of the video rental system that is shown in the context DFD. Read through the diagram, and then we will introduce some of the key concepts based on this diagram. The Video Rental System Data Flow Diagram example contains three processes, two external entities, and two data stores. Although there is no design guideline that governs the positioning of [https://www.visual-paradigm.com/tutorials/data-flow-diagram-example-video-rental-store.jsp](https://www.visual-paradigm.com/tutorials/data-flow-diagram-example-video-rental-store.jsp) Page 1 of 3 Visual Paradigm Data Flow Diagram with Examples-Video Rental System Example Tutorial shapes in a Data Flow Diagram, we tend to put the processes in the middle and the data stores and external entities on the sides to make it easier to comprehend. Based on the diagram, we know that a Customer makes a Video request to the Rent Video process. The Rent Video process also receives Video info. from the Video Library data store. As a result, the process produces a Bill for the Customer and stores the Rental info. in the Rental data store. A Customer can Return a Video by providing Video & Rental info. The process stores the Video info. in the Video Library data store and the Rental info. in the Rental data store. As a result, a Return receipt is delivered to the Customer. Although we said that the receipt is delivered as a result of the Return Video process, the Data Flow Diagram implies no such thing. It is our common sense that leads us to interpret the diagram in the way that we naturally understand it. Strictly speaking, the diagram only tells us that the Return Video process receives Video & Rental info. and produces Video info. , Rental info. , and a Return receipt, with no order specified. Note that a Data Flow Diagram does not answer in what way or in what order the information is used throughout a system. If this information is important and worth mentioning, consider modeling it with diagrams like a BPMN Business Process Diagram or a UML Activity Diagram. Finally, a Manager can receive a Rental report from the Generate Rental Report process, and the information involved is provided by the Rental data store. Data Flow Diagram Tips and Cautions Be Aware of the Level of Detail In this Data Flow Diagram example, the word "info" is used many times when labeling data. We have"rental info" and "video info." What if we were to write them explicitly as "rental date, video rented, person renting," and "video id, video name, and video status"? Is this correct? Well, there is no definite answer to this question, but try to ask yourself a question when making a decision: Why are you drawing a DFD? In most cases, a Data Flow Diagram is drawn in the early phase of system development, when many details have yet to be confirmed. The use of general terminologies like "details," "information," and"credential" certainly leaves room for discussion. Howeve

FAQs

What does a context DFD include for the video rental system example?

A context DFD includes one and only one process representing the system and shows external entities that interact with it, connected by data flow connectors.

How does the level 1 DFD describe customer actions in the example?

It shows the customer making a video request to the Rent Video process, which uses video information from the Video Library store and produces a bill while storing rental information in the Rental store.

Why should you not mix up a data flow diagram with a process flow diagram?

A DFD represents exchange of information; connectors label data flows, not step-by-step process flow. If you need process flow behavior, consider using UML Activity Diagrams or BPMN Business Process Diagrams.

Oct 25, 2026

Upload by Aurelia