Glossary

ABM (Agent-Based Model). A simulation in which autonomous agents interact within a shared environment according to individual decision rules; system-level outcomes emerge from the aggregate of individual actions.

Arena. The self-contained unit of play in BDPD: one commons resource, one set of players, one policy surface. Multiple arenas can coexist inside a World.

Archetype. A behavioural label (e.g. conservative, aggressive) that parameterises a built-in agent’s strategy or nudges an LLM agent’s system prompt. Not a hard constraint on decisions.

Built-in agent. A deterministic heuristic player whose harvest decision is a fixed function of observable state and private parameters. Contrasted with LLM agents, which generate decisions via a language model.

Carrying capacity (\(K\)). The maximum sustainable commons stock under logistic growth when harvest is zero.

Cheap talk. Non-binding, costless communication between agents (Farrell and Rabin 1996). In BDPD, implemented as broadcast messages, private messages, and harvest announcements that carry no enforcement.

Cliff (commons cliff). A rapid, often irreversible collapse of the commons stock below the survival threshold \(\theta\). Characteristic of the Seneca asymmetry: slow growth followed by abrupt decline.

CPR (Common-Pool Resource). A resource system where exclusion is difficult and one agent’s use subtracts from availability to others (Ostrom 1990).

Announce frequency. Governance metric: fraction of (player, turn) pairs in which the agent populated the optional announced field with a non-null intended harvest. Diagnostic for whether the cheap-talk announcement channel is being used at all.

Cooperation index. Governance metric: fraction of players whose actual harvest fell at or below their sustainable per-player share for the turn (within tolerance \(\varepsilon\)). A reading of \(1.0\) means every player restrained.

Engine. The dynamical model that governs how the commons stock evolves each tick. BDPD ships two engines: logistic (single-variable \(S\) with regeneration rate \(r\)) and Seneca (three-variable \(R\), \(C\), \(P\) following Bardi’s ODE system).

Graduated sanctions. Ostrom’s design principle #5: sanctions that escalate with repeated violations rather than applying a fixed penalty. In BDPD, implemented via a ladder vector indexed by violation ordinal.

Junk arena. A designated arena receiving players excluded from their home arena after a pact violation. Structurally identical to any other arena but socially distinct.

Lie score. Governance metric: mean absolute gap between announced and actual harvest, computed only over (player, turn) pairs where an announcement was made. Measured in raw harvest units, so its scale tracks the active pact’s harvest cap.

Link. A directional per-tick flow between two arenas. Link.type = 'resource' transfers commons stock; Link.type = 'pollution' routes a hidden state variable from an emitter to downstream receivers.

Meta-agent. A non-playing observer that reads arena or world state and emits governance actions (sanctions, cap adjustments). Operates at arena scope or world scope.

Defector (Mule). An agent assigned the aggressive archetype that systematically over-extracts relative to the pact cap. The code-level name mule is retained for traceability; in narrative text the papers in this series use defector.

ODE (Ordinary Differential Equation). A differential equation involving functions of a single independent variable (here, time). The Seneca engine integrates a 3-variable ODE system (\(R\), \(C\), \(P\)) at each tick.

OFAT (One-Factor-At-a-Time). A robustness-testing protocol that sweeps one model parameter while holding all others at baseline, repeated for each parameter independently. Does not test parameter interactions.

Pact. A declared agreement among players specifying terms (e.g. harvest_cap, commons_floor). Pacts are soft constraints: violations are detected and may trigger sanctions, but the platform does not prevent the violating action.

Perturbation. An arena-level side-effect triggered by a game event or schedule. Examples: sanction (wealth deduction on pact violation), exclude (player migration to junk arena), capital_shock (multiplicative scaling of capital \(C\)).

Regeneration rate (\(r\)). The intrinsic growth rate of the logistic commons: \(\Delta S = r \cdot S \cdot (1 - S/K) - \text{harvest}\).

Sanction rate. Governance metric: count of sanctions fired in a turn divided by nPlayers. A value of \(1.0\) means every player was sanctioned; under typical pact-violation enforcement, single-fire turns yield \(1/N\).

Seed. The random-number-generator initialisation value for a simulation run. Used to test robustness: a finding that holds across multiple seeds is less likely to be a sampling artefact.

Seneca cliff (Seneca effect). An asymmetric dynamical pattern in which a quantity grows slowly then collapses rapidly. Named after Seneca’s observation that “increases are of sluggish growth, but the way to ruin is rapid.” Formalised by Bardi (2017) as a property of coupled ODE systems with positive feedback on the decline.

Silent defection. Governance metric: fraction of (player, turn) pairs in which the agent skipped the announcement channel (announced = null) and over-harvested relative to its share. Captures the “fly under the radar” failure mode that lie_score misses by construction.

Substrate. The combination of engine, arena topology, link structure, and policy surface that defines the experimental environment. Used interchangeably with “platform configuration.”

Threshold (\(\theta\)). The commons stock level below which the arena is considered collapsed. A gate condition: if \(S_{\text{final}} \leq \theta\), the collective action has failed.

Tick (turn). One discrete time step of the simulation. Within a tick: agents observe state, submit decisions, the engine updates the commons, metrics are computed, perturbations fire.

Treaty. A World-level agreement spanning multiple arenas (e.g. harvest_cap_per_arena_per_round). Observed by world-scope meta-agents and enforced through perturbations.

World. The top-level container holding one or more arenas, their links, treaties, and meta-agents. Introduced in BDPD v1.0 to support nested and polycentric governance structures.