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Extending Multi-Agent Cooperationby Overhearing

Floriano ZiniSRA Division - ITC-irst, Povo (Trento) - Italy

Joint work with

Paolo Busetta, Luciano Serafini

SRA Division - ITC-irst, Povo (Trento) - Italy

Dhirendra Singh

DISA - University of Trento - Italy

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Contents

What is overhearing?

The overhearing architecture

• An experiment

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The Overhearing Pattern

The capability (of an agent) to

listen to a conversation between two or more parties (other agents)

intervene at the right moment by

providing suggestions to the speakers, or

performing actions for them

with the aim of

improving other agents’work, and/or

achieving a personal gain and/or

satisfying a social obligation

...

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Examples

“Give me that pen over there, please!”

“I’ll take it for you”

“Don’t give it away”

SusanMary

Peter

“Use mine”

Susan’s goal is to obtain any pen asap,I’m closer to her than Mary,I have a pen.

I’m closer to the pen than Mary,I’m happy to perform the action forher because I need her help in future

Susan wants to steal the pen!

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Why Overhearing?

achieving extemporary collaboration in a community of artificial agents by means of unobtrusive and unsolicited suggestions

In other words:

shifting from requested to spontaneous help in agents collaborations

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Contents

What is overhearing?

The overhearing architecture

An experiment

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The Overhearing Architecture

Service 1 Service 2

Overhearer

suggester 1suggester 1Suggester

subscriptions

suggestionssuggestions

notifications

communication channel

observations

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The Overhearing Architecture

Overhearing is performed by two agents that play different roles:

Overhearer must be able to classify the overheard communication according to some criteria

appropriately notify it to the suggesters

Suggester must be able to subscribe for the information it is interested to receive

understand the behavior of the service agents

make appropriate suggestions at the appropriate time point

Multiple overhearers, and many suggesters, may be active at the

same time

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Interaction Suggester-Overhearer

A possibility is Ontological Overhearing (paper at ATAL 2001) A suggester formulates its interests using a formalism inspired

by description logics and modal temporal languages The formalism allows the suggester to specify:

• the messages’content, rather than pure syntax• the temporal sequence of communication performatives, i.e. the

development of a conversation The overhearer

logs the conversation between services performs some limited interpretation of the messages passing on the

channel using an ontology notify the suggester according to its interests

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Understanding Agents’Behavior

• Service agents make available a public model of their behavior to help suggesters to understand their current mental state

• The public model may be described as a state machineM = < S, T >– S is a set of mental states, s = < B, D, I >, s S – T is a set of labeled transitions, T S S L– L is a set of labels, each l L denotes an action or an event

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Understanding Agents’behavior

The model may be a not fully accurate representation of an agent’s behavior:• A state contains the representation of the service’s mental

attitudes it wants to be visible• The set T of labels contains the representation of actions and

events the service wants to publicise• The model may contain transitions that are not observable,

because do not correspond to communicative actions or events

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Contents

• What is overhearing?

• The overhearing architecture

• An experiment

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Agent-Search.com

“Give me URL for keyword X”

“URL for X: Y”

Overhearer

Keyword-basedsubscriptions

Topic suggesterTopic suggester

Topic suggester Cache suggester

Queries and URLssubscriptions

User Assistant Referencer

Synonyms and similarities of X

Cached URLs

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Referencer Public Model

Ready to receivea request

Referencer receives request forsearching a keyword K from UA(observable action)

Ready to submit request

Answer available

Referencer asks HTDIG forsearching K(non-observable action)

Request submitted

Referencer receives additionalkeyword Kfrom topic suggester (observable event)

Referencer receives URL fromcache suggestor (observable event)

Request submitted

Referencer asks HTDIG for searchingK1, …, Kn (non-observable action)

References receives additional keywordK from topic suggester(observable event)

Answer availableReferencer receives URL from cachesuggestor (observable event)

Referencer receives answer fromHTDIG (non-observable event)

Answer available

Referencer sends answer toUA (observable action)

Ready to receivea request

User Assistant

Referencer

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Advantages and Disadvantages

• Main advantages: flexibility, enhanceability– Overhearers and suggesters can be plugged in into a running

system– Particularly suitable for: fine tuning of agents instrumented

from the outside; adaptation to specific environments, reuse; additions of certain kinds of functionality: monitoring (including profiling, auditing), recommendations systems…

• Costs: observable communication, state recognition, handling of suggestions

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Conclusions and Future Work

• The overhearing architecture opens up opportunities and challenges in designing and engineering cooperative multi-agent systems

• In the future we are going to investigate some of the following topics in the context of the presented overhearing architecture– computational model for agents– plan / goal / intention recognition– intention revision– extensions to the language for suggester subscription– engineering of a software platform that supports overhearing

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Acknowledgements

We want to thank• Antonia Donà for the revision of the paper• Srinath Anantharaju for the contribution to the implementation

of the demonstrator