Flow
The movement of matter, energy, or messages between components or across boundaries. The substance transfers that keep systems functioning.
Formal Definitions
Mobus & Kalton (2015):
“N is generally a flow network through which real substances are moving from one node (component) to the next with causal influence. The term cap is a function giving a capacity describing the flow rates.”
(Principles of Systems Science, Section 4.3)
“All systems within the Universe are open to input and output flows of at least one of: material, energy, or messages (which are special forms of material/energy flows).”
(Section 3.4.2.1.2.1)
The mathematical formalization: cap_{i.k,l}: C × C → ℝ∞ — a function mapping component pairs to real-valued flow capacities.
Bunge (1979): Bunge captures flow dynamics through the action operator:
“We say that one thing acts upon another if it modifies the latter’s behavior line, or trajectory, or history. The acting of thing a on thing b is symbolized a ⊳ b.”
(A World of Systems, Chapter 1)
Synthesis
Mobus treats flows as fundamental primitives with mathematical capacity functions describing rates of matter/energy/message transfer through network edges. Bunge captures flow effects through action relations (⊳) and behavior modification. Mobus is more explicit about quantification; Bunge emphasizes causal consequences.
Types of Flow
- Material flows: Physical substances moving between components
- Energy flows: Transfers of work capacity (heat, electricity, chemical potential)
- Message flows: Information-bearing patterns (signals, data, symbols)
Key Insight
Every living system requires continuous flows to maintain itself against entropy. When flows stop, systems decay.