Topic 5: Communication and Negotiation Protocols

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Topic 5 Communication and Negotiation Protocols

• Communication and ACLs
• direct vs. indirect communication
• speech act theory
• ACLs - KQML / FIPA-ACL
• Negotiation protocols
• contract-net protocol
• auction protocols
• Notation - AUML

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1. Communication and ACLs

• communication
• the basis for any interaction
• effected through signals

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Direct communication

• message passing
• some of the challenges
• distributed systems
• brokering, naming services, discovery,
• infrastructure for sending messages
• heterogeneous entities
• language, developer, execution environment,
• multi-agent systems
• objects ? messages
• agents ? speech acts
• why something different?

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• an example
• MAS with cognitive of practical reasoning agents
• focus on mental states
• messages must have a meaning to other agents
• e.g. agent 1 sends message to agent 2
  doSomething(x)
• what does this mean to agent 2 ? how
  should/could he respond ?
• agent 1 asks agent 2 to do x ? part of
  negotiation protocol ?
• agent 1 tells agent 2 to do x ? assuming a
  commitment ?
• agent 1 relies on the fact that agent 2 will do x
  ? part of task allocation ?
• agent 1 will do x ?
• does agent 2 think agent 1 is waiting for a reply
  ?
• what is x ? a task ? a question ? the name of an
  agent ?
• does agent 1 asks agent 2 to perform task itself,
  or just make sure the result is achieved
• what must agent 2 do with the result ?
• must be semantically clear

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Agent Communication

• ability to exchange information requires
• 1. ability to physically exchange
  information
• 2. common understanding
• 3. common language
• 4. interaction strategies / protocols

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Agent Communication

• ability to exchange information requires
• 1. ability to physically exchange
  information
• 2. common understanding
• 3. common language
• 4. interaction strategies / protocols

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Agent Communication

• ability to exchange information requires
• 1. ability to physically exchange
  information
• 2. common understanding
• exchanging knowledge requires mutual
  understanding ? 2 keys
• translation between languages
• sharing semantic content
• - each agent has implicit assumptions on its
  own semantics
• - translation must preserve semantics!
• to share knowledge, we must have a common
  semantics
• can be shared via common ontologies
• 3. common language
• 4. interaction strategies / protocols

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Agent Communication

• ability to exchange information requires
• 1. ability to physically exchange
  information
• 2. common understanding
• 3. common language
• incorporates two types of languages
• content language
• communication language Agent Communication
  Language
• 4. interaction strategies / protocols

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Agent Communication Languages (ACL)

• Agents are typically defined at a high level
• an ACL should support intentional communication
• the intentional descriptions use concepts such
  as beliefs, goals, intentions, commitment
• the language should not define protocols such as
• transport protocols
• high level coordination protocols
• constraints on valid exchanges

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Speech Act Theory

• speech act theory views human speech actions
  (John Austin, 1962)
• as in an attempt to influence
• three parts of speech
• locution physical utterance
• illocution the intended meaning
• perlocution the action that results from the
  locution
• use performatives to identify illocutionary force
• example
• Please be quiet!
• locution the actual performance of the act
• illocution the purpose of the utterance
• perlocution the consequences of the utterance

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ACLs FIPA ACL

• Foundation for Intelligent Physical Agents -
  http//www.fipa.org/
• o 1995
• since 2005 IEEE Computer Society standards
  organization
• promotes agent-based technology and the
  interoperability of its standards with other
  technologies
• standardisation of agent-related issues
• FIPA-OS
• FIPA infrastructure architecture
• ...
• FIPA-ACL
• similar to KQML
• consists of a set of message types and the
  description of their pragmatics that is, the
  effects on the mental attitudes of the sender and
  receiver agents.
• describes every communicative act with both a
  narrative form and a formal semantics based on
  modal logic.
• separates the outer language (the intended
  meaning of the message) from the inner language
  (content language).

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ACL Message
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FIPA ACL performatives
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FIPA ACL semantics in SLthe Semantic Language

• SL (Semantic Language)
• can represent propositions, objects, and actions
• formal semantics
• lt message precondition rational
  effect gt
• message the content of the message
• precondition on the situation (mental state) of
  the sender
• rational effect intended effect on mental state
  of receiver

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FIPA - Communicative Acts (1)

• inform
• the sender informs the receiver that a given
  proposition is true.
• confirm
• the sender informs the receiver that a given
  proposition is true, where the receiver is known
  to be uncertain about the proposition.
• disconfirm
• the sender informs the receiver that a given
  proposition is false, where the receiver is known
  to believe, or believe it likely that, the
  proposition is true.
• failure
• the action of telling another agent that an
  action was attempted but the attempt failed
• accept-proposal
• the action of accepting a previously submitted
  proposal to perform an action
• agree
• the action of agreeing to perform some action,
  possibly in the future
• cancel
• the action of cancelling some previously
  request'ed action which has temporal extent (i.e.
  is not instantaneous)
• cfp
• the action of calling for proposals to perform a
  given action.

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FIPA - Communicative Acts (2)

• inform-if
• a macro action for the agent of the action to
  inform the recipient whether or not a proposition
  is true.
• inform-ref
• a macro action for sender to inform the receiver
  that an object corresponds to a definite
  descriptor (e.g. a name).
• not-understood
• the sender of the act (e.g. i) informs the
  receiver (e.g. j) that it perceived that j
  performed some action, but that i did not
  understand what j just did.
• propose
• the action of submitting a proposal to perform a
  certain action, given certain preconditions.
• query-if
• the action of asking another agent whether or not
  a given proposition is true.
• query-ref
• the action of asking another agent for the object
  referred to by an expression.
• refuse
• the action of refusing to perform a given action,
  and explaining the reason for the refusal.

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FIPA - Communicative Acts (3)

• reject-proposal
• the action of rejecting a proposal to perform
  some action during a negotiation.
• request
• the sender requests the receiver to perform some
  action. One important class of uses of the
  request act is to request the receiver to perform
  another communicative act.
• request-when
• the sender wants the receiver to perform some
  action when some given proposition becomes true.
• request-whenever
• the sender wants the receiver to perform some
  action as soon as some proposition becomes true
  and thereafter each time the proposition becomes
  true again.
• request-whomever
• the sender wants an action performed by some
  agent other than itself. The receiving agent
  should either perform the action or pass it on to
  some other agent.
• subscribe
• the act of requesting a persistent intention to
  notify the sender of the value of a reference,
  and to notify again whenever the object
  identified by the reference changes.

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ACLs KQML

• Knowledge Query Manipulation Language (KQML)
• KQML has 3 layers
• content - ignored by KQML messages
• message
• determines interaction types
• supplies performative content
• may describe ontology, etc.
• communication
• low level communication parameters
• sender, receiver, unique message ID

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1. Communication ACLs2. Negotiation protocols

• Basic protocols
• contract-net protocol
• auction protocols

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Negotiation protocols /Market-based Mechanisms

• iterative communication among a group of agents
  in order to reach a mutually accepted agreement
  on something..
• every day approach in resolving conflicts
• needed
• a set of options
• a utility function
• every option has a price and benefit
• this function evaluates the worth of an option to
  an agent.
• a negotiation protocol
• multiple stages or steps in the negotiation
  process
• eventually the process must either terminate or
  converge to a solution

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The Contract Net Protocol

• introduced by R.G.Smith in 1980
• studied extensively with several variations in
  subsequent years.
• how it works
• a manager
• breaks the problem into several interacting
  sub-problems
• looks for a contractor
• selects the suitable contractor
• assigns a sub-problem
• monitors the progress of the overall solution
• a contractor
• bids for work
• accepts a task
• it has a binding agreement to complete the task
  according to the agreed terms
• and completes the task undertaken.
• recursively, the contractor can be a manager for
  the task it has undertaken.
• Basic assumptions

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The Contract Net Protocol
I have a problem!
(b) Task Announcement
(a) Recognising the problem
(c) Bidding
(d) Award Contract
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The Contract Net Protocol
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Applicability of Contract Net

• The Contract Net is
• a high-level communication protocol
• a way of distributing tasks dynamically
• decentralized / situated
• a means of self-organization for a group of
  agents
• but
• limited (mostly for well-defined hierarchies of
  tasks)
• not scalable
• re-allocation ?

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Auctions

• an auction takes place between
• an agent known as the auctioneer
• a collection of agents known as the bidders
• goal
• for the auctioneer to allocate the good to one
  of the bidders
• typically
• the auctioneer desires to maximize the price
• bidders desire to minimize price

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Auction Parameters

• goods can have
• private value
• public / common value
• correlated value
• winner determination may be
• first price
• second price
• bids may be
• open cry
• sealed bid
• bidding may be
• one shot
• ascending
• descending

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Example Auction protocols

• English auction
• parameter values
• first price
• open cry
• ascending
• Dutch auction
• parameter values
• open-cry
• descending
• (first price)
• First-Price Sealed-Bid Auctions
• parameter values
• sealed bid
• one-shot auction
• first price

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English Auctions
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Dutch Auctions
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4. Notation - Agent UML

• a proposal for an agent-oriented modeling
  language
• Pros
• Likely standardization on UML 2.0
• Accepted by FIPA
• Contras
• UML dialect, not necessarily compatible
• AUML
• AUML class diagram
• AUML interaction diagrams
• esp. AUML sequence diagrams

http//www.fipa.org/repository/ips.php3
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FIPA TC C 2000Specifies 11 Protocol
Specifications

• http//www.fipa.org/repository/ips.php3
• FIPA Request Interaction Protocol Specification
• FIPA Query Interaction Protocol Specification
• FIPA Request When Interaction Protocol
  Specification
• FIPA Contract Net Interaction Protocol
  Specification
• FIPA Iterated Contract Net Interaction Protocol
  Specification
• FIPA English Auction Interaction Protocol
  Specification
• FIPA Dutch Auction Interaction Protocol
  Specification
• FIPA Brokering Interaction Protocol Specification
• FIPA Recruiting Interaction Protocol
  Specification
• FIPA Subscribe Interaction Protocol Specification
• FIPA Propose Interaction Protocol Specification

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Summary

• communication
• indirect (later) vs. direct communication
• message-based communication
• ACLs --gt speech act theory
• Negotation protocols
• Notation - AUML