Context Diagram



Definition

Context Diagram
a top-level requirements diagram that documents the external environment of a blackbox system:
Semantic Net Context Diagram
a context diagram drawn as a kind of semantic net showing the general relationships between the system and its externals
Data Flow Context Diagram
a context diagram drawn as a kind of data flow diagram showing the more detailed dataflows and object flows between the system and its externals

Objectives

The typical objectives of a context diagram is to document:

Benefits

The typical benefits of a context diagram are to:

Contents

The typical contents of a context diagram are:

Stakeholders

The typical stakeholders of a context diagram are:

Phases

Preconditions

Context diagrams can typially be started if the following preconditions hold:

Inputs

The typical inputs to a context diagram include:

Guidelines

Conventions

Context diagrams are typically constrained by the following conventions:

Examples

Heating and Cooling System Context Diagram(s)

The following are two system context diagrams for a home heating and cooling system. The semantic net context diagram is on the left, and the corresponding data flow context diagram is on the right. Note that the semantic net version is at a much higher level of abstraction than the data flow version. Note also that the semantic net version answers the question “Why?” whereas the data flow version better answers the question “How?”

Heating and Cooling System Context Diagrams

Digital Thermostat Software Context Diagram

The following semantic net context diagram documents the direct and indirect externals of a blackbox digital thermostat software application. Notice that the indirect externals are critical for understanding the context of the software, whereas the single direct external (the integrated chip) is of little interest except for reminding the architect that the software should be portable.

Digital Thermostat Software Context Diagram

Electronic Auction System Context Diagram

The following system context diagram documents the externals (e.g., human actors, computers, networks, and gateway system) of a blackbox electronic auction system application. It uses the OML notation, which is more understandable than UML for context diagrams.

Electronic Auction System Context Diagram