Glossary · System coordination, integration and orchestration
External system
Also known as: third-party system, external interface partner
German: Externes System
In systems engineering, an external system is a system outside the boundary of the system of interest that interacts with it through defined interfaces, and whose behavior the system of interest can rely on only to the extent agreed in those interfaces.
- System integration
In one sentence
An external system lies outside the system boundary and interacts with it only through defined interfaces and agreed behavior.
Example
For a palletizer supplier, the customer's warehouse management system is an external system that sends pallet patterns and receives pallet IDs.
How it applies
- Systems engineering: Identifying external systems defines the System boundary. Each external system needs an interface definition and documented assumptions about its behavior, availability and data quality.
- Engineering: Design for external systems that are slow, unavailable or send unexpected data. Their failures should lead to a defined state of your system, not undefined behavior.
- Documentation: Context diagrams should show all external systems and interfaces. Manuals should say which functions depend on an external system and what the operator sees when it is unavailable. Responsibility for the external system itself stays with its owner.
External system vs. subsystem
A Subsystem is part of the system of interest and under its design authority. An external system is not; you can specify only the interface, not its internals.