Subsystem
A component inside a system that is itself a system — with its own boundaries, components, and behaviors. Systems nest within systems.
Formal Definitions
Mobus & Kalton (2015):
“Components of a system that are not multisets or atomic components… may themselves be subsystems, that is, having sufficient complexity to warrant further deconstruction.”
(Principles of Systems Science, Section 4.3, Eq. 4.3)
The recursive definition:
“c_{i,j,l} = {S_{i,j,l+1} if component is complex; a if component is atomic}”
This establishes a tree structure where each level of organization contains either decomposable subsystems or atomic primitives.
Bunge (1979): Bunge defines subsystems relationally through the ancestry relation, which forms a strict partial order. Every system of interest (SOI) is embedded in a larger supra-system, and this relationship inverts to define subsystems.
(A World of Systems, Chapter 1)
Synthesis
Mobus treats subsystems as complex components requiring further decomposition, establishing a recursive hierarchy with indexed levels. Bunge emphasizes the mathematical ordering of subsystem-system relationships through strict partial order, ensuring well-defined hierarchies without circular dependencies.
Key Insight
Subsystem decomposition is analytical, not ontological. The “right” level of decomposition depends on the question being asked. A cell is a subsystem of an organ, which is a subsystem of an organism — but each can be studied as a system in its own right.
Explore Further
- Universe as supersystem — Hierarchical nesting at cosmic scale
- Subsystems as change mechanisms — How subsystems drive system dynamics