Context Diagram (DFD Level 0)

CSC-326 · Semester V · System Analysis and Design

beginner20 minAvailable

The whole system as one process surrounded by external entities.

Data flows (click to highlight)

The context diagram shows the system boundary in one diagram — no data stores, no internal detail. Every external entity and its data flows must be traceable into the level-1 decomposition.

Lab brief

Objective

Model the boundary of a system with a context diagram that shows the single process, its external entities and the data flows between them.

Theory & concepts

A context diagram (DFD level 0) is the highest-level view of a system. It shows exactly one process - the whole system - surrounded by external entities such as customers, suppliers or other systems. Arrows represent the data flows that cross the system boundary.

Rendering diagram…

Context diagram: the system, entities and data flows at level 0

The point of the context diagram is to establish scope. Anything that exchanges data with the system but lives outside it is an external entity. Data stores never appear on a context diagram because they are internal implementation details.

Name the single process after the system, e.g. Library System.
Identify external entities that send or receive data.
Draw a data flow for every piece of data crossing the boundary.
Label each flow with a meaningful noun phrase such as Book Request or Fine Notice.

Prerequisites

Lesson: Introduction to system analysis
Lesson: Data flow diagrams

Instructions

1Choose a system, for example an online bookstore or a hospital registration desk.
2List every person or external system that exchanges data with it.
3Place the system as one process in the center.
4Connect each external entity with the data flows it sends and receives.
5Check that no flow is invented and every flow has a label.

Tasks

List the external entities
Name every external entity for your chosen system.
Draw the flows
Sketch each data flow between the entities and the single process.
Defend the boundary
Explain why a candidate flow was excluded or included in the scope.

Self-check

Exactly one process appears, centered and named after the system.
Every external entity connects to the process with labeled flows.
No data store is shown on the context diagram.
The student can justify the system boundary.

Environment

diagram canvasexternal entity shapesflow labelingexport

Context Diagram (DFD Level 0) · System Analysis and Design · Learn CSIT