Law Awareness in a Norm-regulated MAS

Alberto Sardinha

Gustavo Robichez de Carvalho

Rodrigo Paes

Pedro Cunha

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Outline

• Introduction

• Architecture

• Case Study : Supply Chain Management

• Conclusion

• Future Work

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Introduction

• Laws of a multi-agent system are defined at design time

• Static selection severely limits:

– The openness of the system

– The dynamic behavior that agents are expected to exhibit

• This work is concerned with the problem of law evolution awareness

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Law Awareness

• Law Awareness service is a publish/subscribe architecture

– In runtime, this service notifies the catalogued agents of any law modification

• The subscriber (agent) sends a message containing a subscription to the publisher (law awareness service)

– This subscription specifies the conditions under which the publisher will send a message to the subscriber

LawAwareness

Service

Subscriber

Subscription

Notification

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Law Awareness

• The subscriber may send subsequent messages updating the subscription – Every update request or subscription tells the publisher what to

look out for

• We propose a law awareness protocol as a means to agents interact with our service– subscribe-law-awareness

• The sender of this performative requests the service to be notified of law modifications. The condition field limits the kind of information that agents will receive.

– update-subscription • The sender of this performative informs the receiver the new

conditions where the subscription is valid. The condition field limits the kind of information that agents will receive.

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Law Awareness

• We propose a law awareness protocol as a means to agents interact with our service– pause-notifications

• The sender of this performative asks the publisher to stop the notification process.

– restart-notifications • The sender of this performative asks the publisher to continue to

notify law evolution.

– notify-law-evolution • The sender of this performative informs the receiver about the

modification of laws. The content field informs the law variation.

– unsubscribe-law-awareness • The sender of this performative requests the service not to be

notified of law modifications.

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Law Awareness Ontology

Case Study: Supply Chain Management

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Supply Chain Management Scenario

• SCM Model: Direct Sales to Customer

• This model is based on:

– Dell

– TAC SCM

Arunachalam, R. and Sadeh, N. The Supply Chain Trading Agent Competition. Journal of Electronic Commerce Research Applications, 2004.

Chopra, S. et al.. Supply Chain Management – Strategy, Planning andOperations. Published by Pearson Prentice Hall, 2004.

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Supply Chain Management Scenario

• Goals:

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Supply Chain Management Scenario

• Interaction between Manufacturer and Supplier:

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Supply Chain Management Scenario

• Ontolology to describe messages:

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Supply Chain Management Scenario

• Implementation based on Jess

– The knowledge base of the agent is based on RDF triples as a template for unordered facts

(deftemplate triple

(slot predicate)

(slot subject)

(slot object))

– Example of fact in agent knowledge base

(triple

(predicate “ns1#type")

(subject “ns2#ManufacturerOffer")

(object “ns3#Class") )

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Supply Chain Management Scenario

• Knowledge is loaded into agent (OWL to Jess) using XSLT stylesheets:

Gandon, F. and Sadeh, N. Semantic Web Technologies to Reconcile Privacy and Context Awareness. Web Semantics Journal. Vol. 1, No. 3, 2004.

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Supply Chain Management Scenario

• Manufacturer receives a notification of a new Norm

– The norm restricts the number of RFQs that can be sent to a Supplier

• This norm (in OWL) is added to the agent’s KB

• The agent is now aware of the new norm

LawAwareness

Service

Subscriber

Notification

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Supply Chain Management Scenario

• The Norm ontology and the instantiation

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Supply Chain Management Scenario

• Code of the Law Awareness:

(defrule Norm_Awareness

(triple (predicate “ns1#hasRestriction") (subject ?normInstance) (object ?restriction) )

(triple (predicate “ns2#type") (subject ?normInstance) (object ?normType) ) => (assert …) (printout t "Norm type = " ?normType crlf "Norm name = " ?normInstance crlf "will call restriction = " ?restriction crlf))

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Supply Chain Management Scenario

• Code of the VerifyRFQ restriction (in maxRFQs):

(defrule Verify_RFQ

(triple (predicate "ns1#type") (subject ?rfq) (object “ns2#ManufacturerRFQ") ) => (assert (triple (predicate “ns3#hasMessage") (subject “ns4#sendRFQ") (object ?rfq) ) ) (verifyRestriction) (printout t "RFQ = " ?rfq " is restricted by norm " crlf)

)

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Supply Chain Management Scenario

• Code of the VerifyRFQ restriction (in maxRFQs):

(deffunction verifyRestriction () (bind ?numRFQSent (+ ?numRFQSent 1)) (printout t "RFQs Sent = " ?numRFQSent crlf) (if (>= ?numRFQSent 3) then (printout t "Your are not allowed to send RFQs" crlf) ))

Supply Chain Management Scenario

DEMO

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Conclusions

• A first approach to tackle the problem of law evolution awareness

– Provide a publish/subscribe architecture

– Notifies in runtime the modifications of laws

– Provide semantic support for agents

• We also depict the representation of laws using JESS and discuss how agents receive notifications and act according to law modification

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Future Work

• Use ROWL to describe rules (?)

• Include new Norms in more interactions

• Build service architecture with Semantic Web Services