An Extended Alternating-Offers Bargaining Protocol for Automated Negotiation in Multi-agent Systems

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An Extended Alternating-Offers Bargaining
Protocol for Automated Negotiation in Multi-agent
Systems

• P. Winoto, G. McCalla J. Vassileva
• Department of Computer Science
• University of Saskatchewan
• Presented by
• Julita Vassileva

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Automated Negotiation in Multi-agent Systems (MAS)

• Conflict of interest

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Classification of Negotiation

• Protocols
• auctions
• bargaining
• voting, etc.
• Negotiated Items
• single attribute (e.g. price)
• multiple attribute (e.g. price and quality)

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Auctions

• Very efficient, but
• Scheduled in advanced
• Non-negotiable
• Only for price
• Controlled by auctioneer

Alternative Bargaining!!
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Bargaining

• Axiomatic bargaining
• Bargainers provide information (proposals, facts,
  and other arguments)
• Arbitrator sets axioms
• Arbitrator decides outcomes (guaranteed)
• E.g. Egalitarian bargaining solution, Nash
  bargaining solution, etc.
• Strategic bargaining
• Set a protocol, both bargainers agreed on it
• Start bargaining (Bargainers offer proposals)
• Bargainers decide final outcomes (not guaranteed)
• E.g. alternating-offer bargaining

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Alternating-offer Bargaining

• Scenario 1
• Buyer How much?
• Seller 1000.
• Buyer 500?
• Seller 800.
• Buyer 600?
• Seller 700!
• Buyer OK, 700.

Scenario 2 Buyer How much? Seller
1000. Buyer 10. Seller hangs up the phone.
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Alternating-offer Bargaining Space an Example
Unit price
Feasible set
0
quality
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Alternating-offer Bargaining

• Bargaining problem ltX, D, ?1, ?2gt
• X feasible set
• D disagreement
• ? preference order of bargainers 1 and 2.
• Goal achieve x?X
• Solving method backward induction
  (Game-theoretic approach)
• Assumptions
• Perfect rationality
• Perfect foresight

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Modifications

• Asymmetric information (Mudgal Vassileva, 2000)
• With deadline (Sandholm Vulkan, 1999)
• Argumentation (Jennings et. al., 2001)
• Strategic delay (Cramton, 1992)
• Free revisions (non-monotonic counter-offer)
• Social model (trust, friendship)

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Alternating-offer Bargaining Space
Multi-Dimensional Bargaining
How to direct the bargainers from being trapped
into no solution region is an important issue.
Unit price
Feasible set
Buyer I am willing to buy it for 5000 if you
could replace the tires with new one.
0
quality
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Proposed Alternating-offer Protocol

• Argumentation (persuade opponents belief)
• Strategic delay
• Free revision (non-monotonic)
• Range offer (instead of one point offer)

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Strategic delay Argumentation
Argumentation Buyer How much? Seller
1000. Buyer 500? Seller My price is lower
than others. Buyer 700? Seller 1000 is very
cheap. Buyer 800, OK? Seller OK, 800.

• Strategic delay
• Buyer How much?
• Seller 1000.
• Buyer
• Seller 800.
• Buyer hmmm.
• Seller 700!
• Buyer
• Seller 500!
• Buyer 300.
• Seller OK, 300!

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Free revision Range offer
Range offer Buyer How much? Seller
1000. Buyer I cant afford more than
500. Seller 499. Buyer 400, OK? Seller OK,
400.
Free revision Buyer How much? Seller
1000. Buyer 500? Seller 800. Buyer
600? .(Seller got a call) Seller
2000. Buyer What? Seller The market price
increases now.
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Proposed Alternating-offer Bargaining

• Bounded rationality (Simon, 1982)
• Bargaining problem ltX, D, ?1, ?2, I1, I2gt
• I private information about the opponent, world,
  and him/herself.
• Modeling of the opponent
• Belief of I.
• ?i f(Ii) (preference may change during the
  negotiation!)

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Alternating-offer Bargaining Space Influence of
Argument
Unit price
Use argumentation to change sellers acceptable
set (shift in sellers private valuation)
Feasible set
0
quality
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Property of Dynamic Feasible Set in
Single-Attribute Bargaining

• Proposition 4. In a dynamic framework when the
  feasible set S moves dynamically during the
  bargaining process (e.g., due to changes of
  private valuations), then the existence of a
  single-attribute bargaining solution is
  guaranteed if agents are rational, S ? ? and
  ?S/?t lt convergence rate.

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Example of Buyers Utility Functions
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Example of Sellers Utility Functions
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Next Steps

• Comparing the new bargaining protocol to the
  classical bargaining protocol
• Ratio of failure
• Length of bargaining
• Computational cost
• Fairness
• Participation rate

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Conclusion

• A study on the existence of single-attribute
  bargaining solutions has been carried out (see
  the paper)
• Some critical bargaining criteria have been
  pointed out
• A bargaining framework with some modifications
  has been proposed

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THANK YOU!
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