Glossary · Systems engineering and MBSE
Internal block diagram (IBD)
German: Internes Blockdiagramm (IBD)
In SysML, an internal block diagram (IBD) is a structure diagram that shows the internal structure of one block: its parts, their ports and the connectors and item flows (signals, data, energy, material) between them.
- Systems engineering
- Data and interfaces
In one sentence
A SysML internal block diagram (IBD) shows the parts inside one block and how their ports are connected by signal, data or material flows.
Example
The IBD of a robot cell shows the safety PLC connected to the light curtain, door switch and robot controller, with the 'safe stop' signal flowing over a dedicated port.
How it applies
- Engineering: IBDs make interfaces explicit and are a source for Interface requirements and the Interface control document (ICD).
- Safety: Connections relevant to safety functions can be traced from sensor via logic to actuator in the IBD.
- Documentation: Connection and wiring overviews in integration manuals can be derived from the IBD; the documentation team should verify that the published view matches the released model.
- Model quality: Type every port and item flow, including units and value ranges, so the IBD can be checked automatically for incompatible connections.
IBD vs. BDD
See Block definition diagram (BDD). The BDD defines types; the IBD shows connected usages of those types inside one block.
IBDs also help identify single points of failure in signal paths.