Process Modeling - Chapter 5 - Key Definitions - Data Flow Diagrams (DFD)

Oct 25, 2026

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Process Modeling Chapter 5 explains key definitions and how to read and construct Data Flow Diagrams (DFDs). It defines process models, DFD elements (processes, data flows, data stores, and external entities), and naming/drawing principles. The chapter covers balancing across decomposition levels, relationships among context, Level 0, Level 1, and Level 2 diagrams, and alternative data flows. It also outlines steps and guidance for creating context diagrams and DFD fragments from use cases.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages11

Reading Time28 min

AccessFree to download

Key Definitions

Process Model

Data Flow Diagrams (DFD)

Elements of a DFD

Data Flow Diagramming

Using a DFD to Define Business Processes

Relationship among Levels of DFDs

Context Diagram

Level 0 Diagram

Level 1 Diagrams

Level 2 Diagrams

Alternative Data Flows

Creating Data Flow Diagrams

Integrating Scenario Descriptions

Steps in Building DFDs

Creating the Context Diagram

Creating DFD Fragments

Creating the Level 0 Diagram

Creating Level 1 Diagrams (and Below)

| Process Modeling
Chapter 5
Key Definitions
• Process model
• A formal way of representing how a business system operates
• Illustrates the activities that are performed and how data moves among them
• Data flow diagramming
• A common technique for creating process models
• Logical process models describe processes without suggesting how they are conducted
• Physical process models provide information that is needed to build the system
DATA FLOW DIAGRAMS (DFD)
Reading a DFD | | --- | | | | Fatimah AL-Shaikh
دعائكم لي ولوالداي 1 | | Elements ofa DFD
• Process
• An activity or function performed for a specific business reason
• Manual or computerized
• Data flow
• A single piece of data or a logical collection of data
• Always starts or ends at a process
DFD Elements
• Data Store
• A collection of data that is stored in some way
• Data flowing out is retrieved from the data store
• Data flowing in updates or is added to the data store
• External entity
• A person, organization, or system that is external to the system but interacts with it.
Naming and Drawing DFD Elements | | --- | | | | Using a DFD to Define Business Processes
• Business processes are too complex to be shown on a single DFD
• Decomposition is the process of representing the system in a hierarchy of DFD diagrams
• Child diagrams show a portion of the parent diagram in greater detail Fatimah AL-Shaikh
دعائكم لي ولوالداي 2 | Key Definition • Balancing involves insuring that information presented at one level of a DFD is accurately represented in the next level DFD. Relationship among Levels of DFDs Context Diagram • First DFD in every business process • Shows the context into which the business process fits • Shows the overall business process as just one process (process 0) • Shows all the external entities that receive information from or contribute information to the system Level 0 Diagram • Shows all the major processes that comprise the overall system – the internal components of process 0 • Shows how the major processes are interrelated by data flows • Shows external entities and the major processes with which they interact • Adds data stores Fatimah AL-Shaikh دعائكم لي ولوالداي 3 Level 1 Diagrams • Generally, one level 1 diagram is created for every major process on the level 0 diagram • Shows all the internal processes that comprise a single process on the level 0 diagram • Shows how information moves from and to each of these processes • If a parent process is decomposed into, for example, three child processes, these three child processes wholly and completely make up the parent process Level 2 Diagrams • Shows all processes that comprise a single process on the level 1 diagram • Shows how information moves from and to each of these processes • Level 2 diagrams may not be needed for all level 1 processes • Correctly numbering each process helps the user understand where the process fits into the overall system Alternative Data Flows • Where a process can produce different data flows given different conditions • We show both data flows and use the process description to explain why they are alternatives Tip--alternative data flows often accompany processes with IF statements Your Turn • At this point in the process it is easy to lose track of the “big picture”. • Describe the difference between data flows, data stores, and processes. Describe in your own words the relationship between the DFD and the ultimate new application being developed Process Descriptions • Text-based process descriptions provide more information about the process than the DFD alone • If the logic underlying the process is quite complex, more detail may be needed in the form of • Structured English • Decision trees • Decision tables Fatimah AL-Shaikh دعائكم لي ولوالداي 4 CREATING DATA FLOW DIAGRAMS Integrating

FAQs

What is a process model in business system analysis?

A process model is a formal way to represent how a business system operates. It illustrates activities performed and how data moves among them.

What elements are included in a DFD?

A DFD includes processes, data flows, data stores, and external entities. Processes represent activities, data flows represent data movement, data stores hold data, and external entities interact with the system.

How do context, Level 0, Level 1, and Level 2 diagrams relate?

The context diagram shows the system as a single process (process 0) and lists external entities. Level 0 breaks the system into major internal processes. Level 1 decomposes each major process into internal processes, and Level 2 further decomposes Level 1 processes when needed.

Oct 25, 2026

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