In Interaction, properties describe the attributes of multiple agents, their connections, and the institutions or rules governing their relationships. Because outcomes in this domain arise from interdependence, properties must capture the characteristics that shape how agents influence one another. These include action sets, information sets, payoff structures, beliefs, and the institutional constraints that mediate interaction.

Properties in Interaction determine how agents respond to one another, how incentives form, how coordination or conflict emerges, and how equilibrium is defined. They transform ontology (what exists) into usable analytical structure (how those things behave). Without precise properties—who knows what, who can do what, what the rules permit—there is no way to model strategic dependence or relational causation. Identifying these properties explicitly ensures that the domain remains centered on inter-agent influence rather than collapsing into individual decision-making (Choice) or system-level behavior (Aggregation).


This table lays out every property relevant to the Interaction domain, sorted into the seven universal property categories. Each row identifies a property that matters when multiple agents influence one another. It defines the property, explains how it functions in strategic or rule-based environments, shows how it is represented formally, and states why it belongs at this scale. Magnitude, Structure, Dynamics, Constraint, Information, and Evaluation now refer to inter-agent characteristics rather than internal, single-agent features. The Interaction category is populated here—the heart of this domain—because cross-agent influence, incentives, and institutional mediation shape all outcomes. No system-level or aggregate properties appear because those belong to Aggregation.
This table is the complete property set for multi-agent interaction.

Property CategoryPropertyDefinition / MeaningFunctional Role in ChoiceHow It Is Measured or RepresentedOntological Status (why it belongs)
MagnitudePayoff magnitudeNumerical outcome each agent receives for joint actionsAllows agents to compare strategies; drives equilibriumPayoff vectors, utility numbersCore quantity agents respond to in interdependence
MagnitudeAction intensity / effort levelQuantitative measure of how strongly an agent takes an actionAffects others’ outcomes and best responsesScalars or action levelsMatters only because it influences other agents
MagnitudeTransfer/payment sizeHow large any transfers, prices, or penalties areShapes incentives and feasible contractsPayment functions, transfersExists because agents exchange value strategically
StructureInfluence structurePattern of which agents affect which othersDefines who responds to whom; shapes equilibrium formDirected graphs, adjacency matricesFoundational relational structure of the domain
StructureInformation structureWho observes what and whenDetermines beliefs, signaling, and strategic inferenceInformation partitions, signaling graphsEssential pattern of strategic asymmetry
StructureInstitutional/Rule architectureThe rules mapping actions to outcomesShapes incentives, constraints, and feasible strategiesMechanism design mappings, market rulesFormal backbone of interaction settings
DynamicsBelief updating ruleHow agents revise beliefs based on others’ actionsDrives strategy adjustment over timeBayesian updating, learning rulesDynamic property only meaningful with >1 agent
DynamicsStrategic adjustment speedHow quickly agents respond to othersDetermines convergence, cycles, and equilibriaUpdate functions, iterative best responseExists only in a multi-agent world
DynamicsPath dependence of interactionsHow previous moves affect current possibilitiesEnables reputation, punishment, cooperationState variables over historiesDynamic property arising from repeated interaction
InteractionStrategic dependenceHow one agent’s action changes another’s payoffsThe essence of the domain; defines incentivesPayoff interdependenciesCore defining property of Interaction
InteractionComplementarity / substitutabilityWhether actions reinforce or counteract each otherDetermines multiple equilibria, coordination, competitionCross-partial derivatives, payoff curvatureGoverns how strategies relate
InteractionExternalitiesUnpriced spillovers between agentsAffects welfare, incentives, mechanism designOff-diagonal effects in payoff matricesInter-agent influence not mediated by rules
InteractionCommunication channelsHow agents send/receive signalsEnables signaling, cheap talk, persuasionMessage spaces, signaling gamesDefines non-action pathways of influence
ConstraintFeasible action sets (multi-agent)What each agent is allowed to doShapes strategic possibilitiesStrategy sets, feasible strategy profilesMulti-agent version of constraints
ConstraintInstitutional constraintsRules that limit possible outcomes or strategiesPrevents undesired behavior; shapes equilibriaMechanism constraints, legal rulesConstraints exist at collective level
ConstraintParticipation constraintsConditions required for agents to join/acceptLimits mechanism viabilityIndividual rationality constraintsOnly meaningful with multiple agents
InformationBeliefs about other agentsProbabilistic expectations about others’ choicesCentral to equilibrium refinement and strategyBelief hierarchies, priorsFundamental epistemic property of interaction
InformationInformation asymmetryDifferences in what agents knowCore driver of adverse selection, signaling, screeningAsymmetric information setsDefines informational environment
InformationUncertainty about rules or typesNot knowing others’ preferences, types, or constraintsDrives Bayesian games and mechanism designType spaces, distribution over typesAllows higher-order uncertainty
EvaluationPayoff evaluationHow each agent ranks outcomes of joint actionsShapes strategic preferencesUtility vectors, ordinal/comparative rankingsEvaluation extended to outcomes shaped by others
EvaluationStrategic value of informationHow much an agent values knowing somethingChanges incentives to hide, reveal, or distort infoValue of information metricsEvaluation in relational environment
EvaluationWelfare comparisons across agentsNormative ranking of multi-agent outcomesEnables mechanism evaluation, social choiceSocial welfare functionsOnly appears when >1 agent exists