STRATUM: A METHODOLOGY FOR DESIGNING HEURISTIC AGENT NEGOTIATION STRATEGIES

Figures & data

FIGURE 1 Scope of the STRATUM methodology.

FIGURE 2 Stages of the methodology.

TABLE 1 Common Types of Dialogical Capabilities in a Negotiation Encounter

	Capability	Explanation
C1	Make proposals	Proposing potential deals to the counterpart
C2	Accept proposals	—
C3	Reject proposals	—
C4	Present information proactively	An agent may present information in order to influence a counterparty's beliefs, preferences, intentions, etc.
C5	Seek information from a counterpart	Participants may have varying abilities to extract information from one another; for example, due to differing levels of authority in a social structure
C6	Provide information reactively	Agents may have differing capabilities to provide information to one another; some agents may not be able to lie or to answer evasively, for example
C7	Seek to exert pressure on counterpart	An agent might be able to threaten or reward other participants for accepting certain deals (Kraus et al., 1998; Sierra et al., 1998); e.g., using authority
C8	Retract Commitments	Agents may have ability to retract commitments or proposals they have made previously. Retraction has been studied, for example, in argumentation theory (Walton and Krabbe, 1995) and in bargaining (Sandholm and Lesser, 2002)
C9	Withdraw	Truly autonomous agents should have the ability to withdraw from any interaction at any stage. Agents may also have the ability to threaten to withdraw
C10	Re-enter	Some auction protocols allow agents to withdraw from auctions and re-enter them later
C11	Do nothing	Be passive and wait until conditions chance; e.g., until market prices go down or until counterpart concedes because of his time constraints

TABLE 2 Typical Environment Characteristics

Counterparts & Peers

– Aggressiveness: How aggressively is the peer or counterpart buying, selling, or bidding?

– Informativeness: How much does the counterpart or peer know? What information do they have access to?

– Trustworthiness: Can peer or counterpart be trusted to fulfill promises, provide truthful information, etc.?

External Conditions

– Rate of change: Are there patterns that capture change in external conditions, such as resource supply, demand, prices, etc.? What factors are these conditions affected by?

– Competitiveness: How competitive are other agents? (This can be seen as a generalization of the aggressiveness attitude to multiple agents.)

FIGURE 3 Decomposing objective top-down; composing capabilities bottom-up.

TABLE 3 Template for Tactic and Strategy Description

Tactic Name	Tactic 1
Dialogical objective	Get a cheap price for a preferred car model
Method	– Inform the dealer about an offer made by a competing dealer
	– Bargain with the dealer by exchanging offers
Capabilities & sub-tactics used	– Capability C4 to provide information proactively
	– Capability C7 to exert pressure on the car dealer
	– Capability C1, C2, and C3 to make, accept and reject proposals, respectively
Rationality condition	None
Risk	None

FIGURE 4 Abstract view of the methodology.

TABLE 4 Risk-Averse Tactic Specification

Tactic Name	Risk-Averse Tactic (RA)
Dialogical objective	– Avoid buying extra expensive hotel bookings
	– Optimize utility by getting the lengths of customers' visits right
Method	– Buy small number of flight tickets at the beginning
	– Bid on hotels if prices are not very high; otherwise, switch to the other hotel type or change the journey
Capabilities & sub-tactics used	– Ability C1 (making proposals/bids)
	ndash; Ability C5 (seek information) by observing other agents' bidding behavior
	– Ability C11 (do nothing)
Rationality condition	Environment is competitive
Risk	If the environment is noncompetitive, the agent misses out on opportunities to optimize length of trips

TABLE 5 Risk-Seeking Tactic Specification

Tactic Name	Risk-Seeking Tactic (RS)
Dialogical objective	Optimize holiday allocation and take advantage of lack of competition in order to get the hotels it wants
Method	– Buy large number of flight tickets at the start
	– Purchase suitable hotels later, without changing flight bookings
Capabilities & sub-tactics used	– Ability C1 (making proposals/bids)
	– Ability C5 (seek information) by observing other agents' bidding behavior
	– Ability C11 (do nothing)
Rationality condition	– Environment is noncompetitive
	– If hotel prices rise, they eventually stabilize
Risk	– If environment gets competitive, hotel prices rise significantly; as a result, one must either pay high hotel prices or change travel plans and shorten stay, hence wasting travel tickets already bought

TABLE 6 SouthamptonTAC-02 Adaptive Strategy

Tactic Name	SouthamptonTAC-02 Adaptive Strategy
Dialogical objective	Maximize utility by adapting to changes in the environment
Method	– If environment is competitive, use the risk-averse tactic
	– If environment is noncompetitive, use risk-seeking tactic
	– If environment is semicompetitive, use medium-risk tactic
Capabilities & sub-tactics used	– Risk-Averse Tactic
	– Risk-Seeking Tactic
	– Medium-Risk Tactic
Rationality condition	—
Risk	—

FIGURE 5 Relationships between attitudes.

FIGURE 6 Methodology models mapped in IBN.

TABLE 7 Description of an Example IBN Strategy

Strategy name	S1
Dialogical objective	Cause counterpart to intend a deal that is more preferable to me
Method	– Find out what deal the counterpart currently wants, call it D
	– Find out what goal D is intended to achieve
	– Assert that D′ also achieves that goal
	– Offer deal D′
Capabilities & sub-tactics used	– Capability C5 (seek information)
	– Capability C4 (present information proactively)
	– Capability C1 (make a proposal)
Rationality condition	– Deal D′ must be acceptable to me, and more preferred to me than deal D
Risk	—

TABLE 8 Tactic Description of an IBN Tactic

Tactic name	T1
Dialogical objective	Cause counterpart to abandon some intended deal D
Method	– Ask the counterpart whether it intends some goal g′
	– Argue that D has the undesirable side-effect of precluding g′
Capabilities & sub-tactics used	– Ability to provide information about consequences
Rationality condition	—
Risk	—

TABLE 9 Description of an Example IBN Strategy

Strategy name	S2
Dialogical objective	Cause the counterpart to intend a deal that is more preferable to me
Method	– Find out what deal the counterpart currently wants, call it D
	– Find out what goal D is intended to achieve, call this goal g
	– Assert that D′ also achieves that goal
	– Cause counterpart to no-longer intend D
	– Offer deal D′
Capabilities & sub-tactics used	– Capability C5 (seek information)
	– Capability C4 (present information proactively)
	– Tactic T1 to cause counterpart to abandon D
	– Capability C1 (make a proposal)
Rationality condition	– Deal D′ must be acceptable to me, and more preferred to me than deal D
Risk	– After abandoning deal D, the counterpart may still not accept deal D′ for some other reason. As a result, if our agent prefers accepting D to nothing, and it is not possible to persuade the counterpart to intend D again, then our agent is worse off

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