Concurrent Programming for DAI

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Concurrent Programming for DAI

• Gul A. Agha Needem Jamali

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Concurrent Programming

• Concurrent programming introduces many
  challenges
• A key challenge is the difficulty of programming
  parallel and distributed architectures
• Some models are very low-level (shared variables
  model).
• One approach would be to use concurrent objects
  in a reflective architecture.
• Using agent programming is such an architecture.

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Patterns of Concurrent Problem Solving.

• Three common Patterns
• Pipelined Concurrency
• Enumeration of potential solutions and the
  concurrent testing of these solutions.
• Divide and Conquer
• Concurrent elaboration of different sub problems
  and joining the solutions.
• No interaction between the procedures.
• Cooperative problem solving.
• Processes dynamically interact in order to solve
  the problem.

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Agent Programming Paradigms

• A few agent programming languages
• Agent Oriented Programming (AOP).
• Concurrent MetateM.
• Telescript.
• Actors.
• I will present all four, with a focus on Actors.

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Agent Programming Paradigms

• A few agent programming languages
• Agent Oriented Programming (AOP).
• Introduction to Multiagent Systems (Wooldridge).
• An Overview of Agent Oriented Programming
  (Shoham).
• Concurrent MetateM.
• Telescript.
• Actors.

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Agent Oriented Programming (AOP)

• Due to Yoav Shoham (Stanford).
• Based on cognitive and societal view of
  computation.
• An agent is an entity that functions continuously
  and autonomously in an environment in which other
  agents exist.
• An agents state is viewed as consisting of
  mental components such as beliefs, capabilities,
  choices, commitments and desires.
• Agenthood is in the mind of the programmer.
• What makes a system - an agent, is the fact that
  one has chosen to analyze and control it in these
  mental terms.

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Agent Oriented Programming AGENT0

• Shoham has developed a basic programming
  language to support AOP AGENT0.
• An agent is specified in terms of four sets
• Capabilities (Things the agent can do).
• Initial beliefs (Things the agent
  knows/believes).
• Initial Commitments.
• Commitment rules.

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Agent Oriented Programming AGENT0 - 2

• The component which determines how the agent acts
  is the commitment-rules set.
• A commitment rule consists of three components
• A message condition.
• A mental condition.
• An action.
• The rule fires if the agent received a message
  that matches the message condition, and the
  agents beliefs match the mental condition.
• The agent than becomes committed to the action.

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Agent Oriented Programming AGENT0 - 3

• An action may be private (sends no message), or
  communicative(sends messages).
• Messages are constrained to three type
• Request.
• Unrequest.
• Inform.

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Agent Oriented Programming AGENT0 Example

• A commitment rule example
• COMMIT(
• ( agent, REQUEST, DO(time, action)
• ), msg condition
• ( B,
• now, Friend agent AND
• CAN(self, action) AND
• NOT time, CMT(self, anyaction)
• ), mental condition
• self,
• DO(time, action) )

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Agent Oriented Programming AGENT0 Main Loop

1. Read all current messages, update beliefs, and
   hence commitments when necessary.
2. Execute all commitments for the current cycle
   where the capability condition of the associated
   action is satisfied.
3. Goto (1).

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AOP - Properties of the Agents Components

• The programmer may assume several properties of
  the agents components
• Internal consistency.
• Good faith.
• Introspection.
• Persistence of mental state.

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Agent Programming Paradigms

• A few agent programming languages
• Agent Oriented Programming (AOP).
• Concurrent MetateM.
• Introduction to Multiagent Systems (Wooldridge).
• Telescript.
• Actors.

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Concurrent MetateM

• Due to Michael Fisher.
• Based on the direct execution of logical
  formulae.
• An agent is programmed by giving it a temporal
  logic specification of the behavior it should
  exhibit.

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Concurrent MetateM - Execution

• Agents execution
• Iteratively build a logical model for the
  temporal agents specification.
• It is possible to prove that the procedure used
  to execute an agent specification is correct.
• If it is possible to satisfy the specification,
  then the agent will do so.

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Concurrent MetateM Agent Structure

• Communication through broadcast message passing.
• An agent has two main components
• An interface
• Computational engine

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Concurrent MetateM Agent Structure - Interface

• The interface consists of three components
• Unique Agent ID.
• Environment propositions.
• Component propositions.
• Example Stack(pop, push)popped, full.

Agent ID
Component propositions
Environment propositions
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Concurrent MetateM Agent Structure - Engine

• An agent specification is given as a set of
  program rules, which are temporal logic of the
  formulae of the form
• antecedent about the past
• ? consequent about present and future.
• The name of the paradigm Declarative past and
  imperative future.

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Concurrent MetateM Syntax

• PML Propositional MetateM Logic.

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Concurrent MetateM Syntax Example