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Individual Plans from Team Plans using Petri Nets

• Afiya Kassim-100307450• akassim@connect.carleton.ca

• Presentation based on paper: From Team Plan to Individual Plans: a Petri Net-based Approach, Bonnet-Torres and Tessier, in AAMAS’05, Netherlands, pg 797-804, 2005.

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Outline

• Introduction• Notion of Agenticity• Team Plans• Abstracting the Team Plan• Example • Conclusion

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Introduction

• Motivation: Team planning is a difficult problem

• Framework for representing a team plan • Projection of team plan on individual

agents• This paper addresses the notion of

activity planning using petri-nets

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Agenticity Hierarchy

Agenticity Hierarchy(depth of the agent in the hierarchy)

Agents implemented to carry out the mission are organized hierarchically in a

team

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Degree of an Agent

• Degree is the largest agenticity of the individual agents that belong to this agent

• An elementary agent has a degree of zero

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Goals

• An elementary goal is one such that there is a specification of the course of actions to be performed by an agent(composite or individual), resulting in the achievement of the goal

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Team Plan

• A team plan is designed in terms of a detailed sequence of tasks, represented as a petri-net

Source(Introduction of agents) and Sink(Removal of agents)

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Analysing Team Plan

Fork Join

Rearrange

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Analysing Team Plan

ChoiceTransfer

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Rules for Abstracting the Team Plan

Reduction of Late Arrival

• Preserves the level of agenticity• Token is modified to encompass the newly introduced agent

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Rules Cont’d

Reduction of Early Withdrawal

• Preserves the level of agenticity• Token is modified

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Rules Cont’d

Fusion of Consecutive Activities

• Transposition of the substitution rule for consecutive places in ordinary Petri nets• Preserves the level of agenticity• Token is not modified

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Rules Cont’d

Fusion of Choice Between Activities

• Preserves the level of agenticity• Token is modified to bear the different possible agenticity sub-hierarchies• Agent is tagged showing there are multiple possible organising structures

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Rules Cont’d

Fusion of Parallel Activities

• Derived from the implicit place suppression rule in ordinary Petri nets• Decreases the level of agenticity• Token is modified

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Rules Cont’d

Reduction of Agent Transfer

• Preserves the level of agenticity• Tokens are modified• Pt is split rule 1 and rule 2 is then applied on the two separate branches

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Example

Team Plan

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Example

Reduction of Team Plan

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Projection of the Team Plan on agent d

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Conclusion

• No discussion on team plan creation• How tokens are created or modified?• Future work: Handling re-planning within

the team in the event of a failure or an external action

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References

• O. Bonnet-Torres, C. Tessier. “From Team Plan to Individual Plans: a Petri Net-based Approach”, In AAMAS’05, Utrecht, Netherlands, 797-804, July 2005.