System Context Diagram - Building Blocks

Building Blocks

Context diagrams can be developed with the use of two types of building blocks:

• Entities (Actors): labeled boxes; one in the center representing the system, and around it multiple boxes for each external actor
• Relationships: labeled lines between the entities and system

For example, "customer places order." Context diagrams can also use many different drawing types to represent external entities. They can use ovals, stick figures, pictures, clip art or any other representation to convey meaning. Decision trees and data storage are represented in system flow diagrams.

A context diagram can also list the classifications of the external entities as one of a set of simple categories (Examples:), which add clarity to the level of involvement of the entity with regards to the system. These categories include:

• Active: Dynamic external entities which frequently initiate events to achieve some goal or purpose (Examples: "Article readers" or "customers").
• Passive: Static external entities which infrequently interact with the system (Examples: "Article editors" or "database administrator").
• Cooperative: Predictable external entities which are used by the system to bring about some desired outcome (Examples: "Internet service providers" or "shipping companies").
• Autonomous (Independent): External entities which are separated from the system, but affect the system indirectly, by means of imposed constraints or similar influences (Examples: "regulatory committees" or "standards groups").