Agent%20Communications:%20Static%20Protocols

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Agent CommunicationsStatic Protocols

• CPSC 601.68/CPSC 599.68
• Rob Kremer
• Department of Computer Science
• University of Calgary

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Static (Ad-hoc) Protocols

• Merely scripts that the agent follows
• Typical notation is state diagrams
• Petri nets are a generalization of state diagrams

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Ad-hoc Protocols Petri Nets
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Simple Petri Nets
Place
Arc
Transition

• Directed arcs only
• Strictly bipartite
• Tokens occupy places (a place can contain any
  number of tokens)
• A transition can fire only when there is
  sufficient tokens at all of the incoming places.
• The transition firing consumes tokens at the
  incoming side and emits tokens to the places on
  the outgoing side.

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Transitions

• If ALL of a transitions incoming places have
  tokens, it MAY fire
• So if theres a single token to available for
  more than one transition, only one of them MAY
  fire

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Transitions

• A transition will place tokens on all of its
  outgoing places IF it fires

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Transitions

• EVERY incoming place must have sufficient tokens
  available in order for it to fire

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Transitions

• Places can contain any number of tokens

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• Lots of other kinds of Petri Nets
• Weighted Petri nets
• Coloured Petri nets
• Hierarchy
• Vector addition system with states
• Prioritised Petri nets
• Timed Petri nets
• Stochastic Petri nets
• etc.
• Could do the whole course on Petri Nets!
• A decent quick description is on Wikipedia at
  http//en.wikipedia.org/wiki/Petri_net

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Example call for proposals
A MIP-net (Multi-agent Interaction Protocol net)
combining two A-nets (Agent nets) and one
IP-net (Interaction Protocol net). Reference Se
a Ling Seng Wai Loke. A Formal Compositional
Model of Multiagent Interaction. AAMAS03
International Conference on Autonomous Agents and
Multi-Agent System, July 14-18, 2003, Melbourne,
Australia. ACM, 2003. Also available
http//delivery.acm.org/10.1145/870000/860791/p105
2-ling.pdf?key1860791key22595358611colldlAC
MCFID15151515CFTOKEN6184618
Ling Loke 2003, p.1053
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Example A produce Protocol
This is an extension of colored Petri nets called
reference nets Reference Lawrence Cabac,
Daniel Moldt Heiko Rolke. A Proposal for
Structuring Petri Net-Based Agent Interaction
Protocols. Lecture Notes in Computer Science
24th International Conference on Application and
Theory of Petri Nets, Eindhoven, Netherlands,
June 2003. Springer, 2003. Also available
http//www.informatik.uni-hamburg.de/TGI/mitarbeit
er/wimis/cabac/netcomponents.pdf.gz
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Issues

• Rigid and Brittle
• Hard to account for all eventualities
• See assignment 1 to convinceyourself of this