Yellow pages and Interaction Protocols

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1 Yellow pages and Interaction Protocols Fabiano Dalpiaz Agent-Oriented Software Engineering (AOSE)

2 Yellow pages How do you look for someone providing a service? Either you know a service provider......or you use yellow pages! How does an agent look for a service? Either it knows another agent that provides that service......or it uses yellow pages! JADE: Yellow pages system implemented via a particular agent called Directory Facilitator (DF) F. Dalpiaz - AOSE

3 Yellow pages How do you let other people know you want to offer a service? Contact the yellow pages owner and ask for publishing an ad How does an agent let other agents know the services it provides? Contacts the Directory Facilitator and registers its services......so that other agents can find its services F. Dalpiaz - AOSE

4 Yellow pages (Directory Facilitator) F. Dalpiaz - AOSE

5 Interacting with a Directory Facilitator (DF) The DF is an agent and as such it communicates using ACL The ontology and language that the DF understands are specified by FIPA It is possible to search/register to a DF agent of a remote platform The jade.domain.dfservice class provides static utility methods that facilitate the interactions with the DF register() modify() deregister() search() The JADE DF also supports a subscription mechanism F. Dalpiaz - AOSE

6 Registering to a DF When an agent registers with the DF it must provide a description (jade.domain.fipaagentmanagement.dfagentdescription) The description is composed of The agent AID A collection of service descriptions (class ServiceDescription) In turn, ServiceDescription is composed of The service type (e.g. Weather forecast ) The service name (e.g. Meteo-1 ) The languages, ontologies and interaction protocols that must be known to exploit the service A collection of service-specific properties in the form key-value pair F. Dalpiaz - AOSE

7 Registering to a DF F. Dalpiaz - AOSE

8 Searching for a service When an agent searches/subscribes to the DF it must specify another DFAgentDescription that is used as a template e.g.: I look for a weather forecast service in italian The DF will compare the existing services to the template Matches represent adequate providers Matches are returned to the searching agent F. Dalpiaz - AOSE

9 Searching for a service DFService.register(template); Note the use of the myagent protected variable: each behavior has a pointer to the agent that is executing it. F. Dalpiaz - AOSE

10 Exercise 1: forecast providers Create a weather forecast MAS Several forecast providers offer forecast services (at least 2) They have different accuracy rates Each provider registers its services to the DF A client agent looks for a weather forecast provider It looks for the most accurate service Providers fails with a certain probability (no information available) [The client chooses another provider until it gets an information] Run the MAS F. Dalpiaz - AOSE

11 Interaction protocols: an example PAgent DF Wrapper Search Engine keyword Search for wrappers Wrappers list Result set Service request (Q) Query (Q) 11 F. Dalpiaz AOSE

12 Interaction protocols Standard sequences of messages types (INFORM, REQUEST, PROPOSE...) that allows specifying predefined sequences of messages exchanged by agents during a conversations. These are known as Interaction Protocols FIPA interaction protocols 12 F. Dalpiaz AOSE

13 Propose

14 Request

15 Subscribe

16 Contract Net

17 Interaction protocols in JADE The jade.proto package contains behaviours for both the initiator and responder role in the most common interaction protocol: FIPA-request (AchieveREinitiator/Responder) FIPA-contract-net (ContractNetInitiator/Responder) FIPA-subscribe (SubscriptionInitiator/Responder) All these classes automatically handle the flow of messages checking that it is compliant to the protocol and the timeouts (if any) They provide callback methods that should be redefined to take the necessary actions when e.g. a message is received or a timeout expires. 17 F. Dalpiaz AOSE

18 Protocols in JADE 18 F. Dalpiaz AOSE

19 Exercise: Request-Interaction protocol Implement a simple request-interaction protocol Weather forecast scenario: who can provide me with the weather for tomorrow? An initiator sends a request to three participants Phase 1: Participant 1 agrees Participant 2 agrees Participant 3 refuses Phase 2: Participant 1 fails Participant 2 succeeds (inform-result) 19 F. Dalpiaz AOSE

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