MultiTier Communication Abstractions for Distributed MultiAgent Systems

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Multi-Tier Communication Abstractions for
Distributed Multi-Agent Systems

• Michael Thome mthome_at_bbn.com

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Motivation

• Problem
• Applications naturally imply multiple levels of
  interaction abstractions
• Cramming multiple levels into a single
  implementation protocol is inefficient
• Optimal use of CPU versus Bandwidth is difficult
  with a single solution
• Solution
• Parallel mechanisms tailored to different
  abstractions
• Coordinated, interacting mechanisms allow for
  balanced resource use

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Observations
An Agent as a model of a business logic
element Fine-grain, tightly-coupled, anonymous
An Agent as a model of a real
entity Coarse-grain, asynchronous/loosely-coupled
, addressable
A model of interacting element sets Group
semantics, group addressable, peering
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The Cougaar Solution

• A Plugin is
• Atomic unit of business logic/opaque processing
• An Agent is
• A set of Plugins
• An identity (name, address, db key, creds)
• A common infrastructure
• A Community is
• A named, addressable group of agents
• Maintained by another agent as a service

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Technical approach

• Plugin
• Tightly coupled, sequential, influence restricted
  to an agent
• Implemented using shared memory, transactional
  blackboard
• Agent
• Agents generally are loosely-coupled, operate in
  parallel, interacts as peer to other agents
• Implemented using message passing
• Community
• Partially-specified addressing, collective
  behavior
• Group-level semantics and dialects
• Implemented as an orthogonal application

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Example a Large Cougaar application

• Entities
• 40 CPUs
• 589 Agents
• 12465 Plugins (50 classes)
• Interactions
• 670K agent-agent messages
• 16M plugin-plugin interactions (24i/m)

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Example an Agent network
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Example a Plugin network
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Example Communities of Agents
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Conclusion

• A hybrid of shared-memory blackboard interactions
  for tightly coupled members and distributed
  message-passing interactions for loosely coupled
  members is an effective and efficient solution
  for complex DMAS applications

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For more information

• BBN Technologies http//www.bbn.com
• Cougaar http//www.cougaar.org
• CougaarForge http//cougaar.org
• UltraLog http//www.ultralog.net
• Other KIMAS03 papers
• An Infrastructure for Adaptive Control of
  Multiagent Systems, Kleinmann, et al
• Multi-resolutional Knowledge Representation for
  Logistics Systems using Prototypes,Properties and
  Behaviors, Berliner, et al

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Backup slides
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Whats a Cougaar?

• Primary Application
• Military Logistics Planning and execution
• Very deep, wide, and complex domain
• Cougaar
• DMAS infrastructure tuned for app
• Java, OSS, general purpose
• UltraLog
• Making Cougaar Applications survivable
• Robust, secure, Scalable adaptively

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Alternate Community view