View
214
Download
0
Embed Size (px)
Citation preview
23-04-19 1
Computer Science
Agent Communications:Static Protocols
CPSC 601.68/CPSC 599.68Rob Kremer
Department of Computer ScienceUniversity of Calgary
23-04-19 CPSC 609.68/599.68: Agent Communications 2
Static (Ad-hoc) Protocols
Merely “scripts” that the agent follows
• Typical notation is state diagrams• Petri nets are a generalization of state diagrams
23-04-19 CPSC 609.68/599.68: Agent Communications 3
Ad-hoc Protocols: Petri NetsBuyer: Request to Buy
Seller: Request PaymentSeller: Accepting to Sell
Buyer: Accepting to Pay
Buyer: Paying for item
Seller: Accepting Payment
Seller: Handing out item
Buyer: Accepting item
Success
23-04-19 CPSC 609.68/599.68: Agent Communications 4
Simple Petri Nets
“Place”
“Transition”
“Arc”
• 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.
23-04-19 CPSC 609.68/599.68: Agent Communications 5
Transitions
• If ALL of a transition’s incoming places have tokens, it MAY fire
• So if there’s a single token to available for more than one transition, only one of them MAY fire
23-04-19 CPSC 609.68/599.68: Agent Communications 6
Transitions
• A transition will place tokens on all of it’s outgoing places IF it fires
23-04-19 CPSC 609.68/599.68: Agent Communications 7
Transitions
• EVERY incoming place must have sufficient* tokens available in order for it to fire
23-04-19 CPSC 609.68/599.68: Agent Communications 8
Transitions
• Places can contain any number of tokens
23-04-19 CPSC 609.68/599.68: Agent Communications 9
• 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
23-04-19 CPSC 609.68/599.68: Agent Communications 10
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:
Sea Ling & Seng Wai Loke. A Formal Compositional Model of Multiagent Interaction. AAMAS’03 – 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/p1052-ling.pdf?key1=860791&key2=2595358611&coll=&dl=ACM&CFID=15151515&CFTOKEN=6184618 Ling & Loke 2003, p.1053
23-04-19 CPSC 609.68/599.68: Agent Communications 11
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/mitarbeiter/wimis/cabac/netcomponents.pdf.gz
23-04-19 CPSC 609.68/599.68: Agent Communications 12
Issues
• Rigid and Brittle
• Hard to account for all eventualities
• See assignment 1 to convinceyourself of this