Multi-Tier Communication Abstractions for Distributed Multi-Agent Systems Michael Thome

1 Oct 2003KIMAS032 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

1 Oct 2003KIMAS033 Observations An Agent as a model of a “real” entity: Coarse-grain, asynchronous/loosely-coupled, addressable An Agent as a model of a business logic element: Fine-grain, tightly-coupled, anonymous A model of interacting element sets: Group semantics, group addressable, peering

1 Oct 2003KIMAS034 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

1 Oct 2003KIMAS035 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

1 Oct 2003KIMAS036 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)

1 Oct 2003KIMAS037 Example: an Agent network

1 Oct 2003KIMAS038 Example: a Plugin network

1 Oct 2003KIMAS039 Example: Communities of Agents

1 Oct 2003KIMAS0310 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

1 Oct 2003KIMAS0311 For more information… BBN Technologies: Cougaar: CougaarForge: UltraLog: 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

1 Oct 2003KIMAS0312 Backup slides

1 Oct 2003KIMAS0313 What’s 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

1 Oct 2003KIMAS0314 Alternate Community view