Flow Gate or Valve Rule¶

Rule — instantiates Conserved Reservoir-Flux Balancing

A control rule that opens, throttles, or closes a flux channel on a defined trigger, steering the network's balance by adjusting flows in real time rather than cleaning up after.

A Flow Gate or Valve Rule binds a conditional rule to one specific flux channel: when a trigger fires — a level, a rate, a schedule — the gate changes that channel's throughput, opening it, throttling it to a set rate, or closing it. The idea that makes it this mechanism: it is the archetype's actuator — the only mechanism here that actually changes a flow rather than measuring, modeling, or auditing one — and it is inherently directional. A valve governs one direction of flux, not the whole balance, which makes the boundary it enforces intentionally asymmetric. It steers a stock back toward bounds at the exact channel where imbalance enters, in real time.

Example¶

Consider freeway ramp metering. The conserved stock is the number of vehicles on a freeway segment; past a critical density it collapses into stop-and-go. A ramp meter is a valve on the on-ramp inflow channel: the rule reads mainline density and releases cars from the ramp at a metered rate that holds total inflow below the point that would tip the segment into a jam. The boundary is asymmetric by construction — the meter can throttle inflow, but it cannot pull cars off the freeway. The result is real: mainline density stays below jam, and throughput actually rises. But the queue backs up on the ramp — the rule relocates part of the load rather than removing it, which is precisely its honest limitation and the thing its tuning must respect.

How it works¶

Bind the rule to one channel and one direction — the valve is asymmetric by design; it acts on inflow or outflow, not the net balance.
Specify trigger and response — a level, rate, or time condition, mapped to open / throttle-to-rate / close.
Choose the control law — bang-bang (fully open or closed) or proportional (meter toward a target rate).
Include a release condition so the gate reopens once the protected stock recovers, rather than latching shut.

Tuning parameters¶

Trigger threshold — the level or rate that actuates the gate. Acting earlier is gentler on the protected reservoir but intervenes more often.
Control law — on/off versus proportional metering; proportional is smoother but needs a trustworthy rate signal.
Throttle setpoint — the rate the channel is held to; the core dial trading the upstream queue against downstream protection.
Asymmetry — which direction the valve governs, and whether an emergency bypass exists for the direction it normally blocks.
Anti-oscillation — a minimum dwell time or hysteresis so the gate does not chatter open and closed near the threshold.

When it helps, and when it misleads¶

Its strength is acting in real time at the precise channel where imbalance enters, holding a stock within bounds without redesigning the system around it.

It misleads because a gate does not remove load — it relocates it. Throttling an inflow propagates the constraint upstream as backpressure^[1], filling the upstream buffer instead; if that buffer is smaller, or the burden lands on a party who did not cause the imbalance, the "fix" is worse than the problem. Aggressive gates oscillate, and a valve tuned to protect one reservoir can starve or flood the next one down the line. The discipline is to check where the throttled flux actually goes and whether the upstream buffer can hold it — pairing the gate with a headroom view of the whole chain, not just the reservoir it guards.

How it implements the components¶

Flow Gate or Valve Rule realizes the intervention side of the machinery — the lever that changes a flux:

flux_intervention_lever_catalog — the gate is a lever from this catalog, defining a concrete open / throttle / close action on a named channel.
asymmetric_flux_boundary — the valve governs one direction of flux only, an intentionally one-way boundary on the channel.

It does not sense the level or rate that triggers it (stock_level_signal) — that's Capacity Headroom Alert, whose signal it consumes; and it does not model the downstream consequences of throttling (scenario_simulation_model) — that's System Dynamics Simulation.

Instantiates: Conserved Reservoir-Flux Balancing — the valve rule is the archetype's hands: the lever that keeps a stock inside its bounds.
Consumes: Capacity Headroom Alert supplies the level/rate trigger that tells the gate when to act.
Sibling mechanisms: Capacity Headroom Alert · System Dynamics Simulation · Material Flow Analysis · Mass-Balance Table · Compartment Model · Data Lineage Balance Check · Inventory Reconciliation Workflow · Loss-Sink Audit · Reservoir Balance Dashboard · Sankey Flow Map · Stock-and-Flow Diagram · Unit Conversion Crosswalk · Water or Resource Budget

References¶

[1] Backpressure — the pattern where restricting a downstream flow propagates the constraint upstream, filling the upstream buffer rather than the downstream one. Borrowed from fluid and network systems, it is why a valve rule relocates imbalance instead of removing it, and why the upstream reservoir's headroom must be checked before throttling. ↩