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Multi-agent system for web services

This overview discusses the implementation and future work of a multi-agent system for web services using the MWS framework. It explores the background of web services and the progression of internet technologies, including HTML, XML, and RDF. It also delves into the concepts of ontologies and semantic web technologies. The MWS framework, based on DAML, serves as a shopping mall for personal agents, providing a directory of web services categorized by products. The implementation of this system is demonstrated with sample services and agents.

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Multi-agent system for web services

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  1. Multi-agent system for web services John Akinyele

  2. Overview • Introduction • Background • MWS • Implementation • Discussion • Future Work • Related Work • Conclusion

  3. Introduction • Web services • a new breed of web application that are self-contained, self-describing, modular applications that can be published, located, and invoked across the web • Web services are a result of the evolving internet/web technologies • Progression of internet technologies • HTML – Semantic Web

  4. Introduction • HTML • The initial language used for developing web pages • It is describes the presentation of the document • It limits the development of automated applications that access them. • XML • Extension of HTML • Allow developers to create their own tag definitions • Lacks global consistency

  5. Introduction • RDF • specifications provide a lightweight ontology system to support the exchange of knowledge on the Web • An ontology - an explicit formal specification of how to represent the objects, concepts and other entities that are assumed to exist in some area of interest and the relationships that hold among them • provides a means through which web sites with meaningful and globally consistent contents can be defined.

  6. Introduction • RDF • A basis for semantic web technologies • semantic web is the idea of having data on the web defined and linked in a way that it can be used by machines for various applications

  7. Introduction • MWS • “Shopping mall” for personal agents • Contains a directory of services providing various web services • Web services are define with a semantic web ontology based on DAML • The directory is categorized by the type of product being offered

  8. Background • DAML • DARPA Agent Markup Language • An extension to XML and RDF by using ontologies to provide a powerful way to describe objects and their relationships to other objects • It has been tested in various applications: • ITTALKS • Webscripter

  9. Background • DAML Services • Enable the creation of services that have particular properties which software agents can discover, invoke, compose, and monitor • Service object is the upper ontology for web services.

  10. Background • DAML Service Object • It seeks to answer 3 questions • What does the service require? • How does the service work? • How is the service used? • It has 3 properties • presents – Service Profile • describedBy – Service Model • support – Service Grounding

  11. Background • DAML Service Profile • Describes what service requires • Parameters, contact information etc • 2 important subclasses • Advertisement • Used to “advertise” the services provided within a service • Request • Used to “declare” what the agent seeks

  12. Background • DAML Service Model • Defines how the service works • Describes the necessary parameters – input and output, and the produced effect • the “stub” or “skeleton” of the methods/objects of the service. • Can represent methods/objects implemented in a wide variety of application domains

  13. Background • DAML Service Model • The process ontology includes • Process • CompositeProcess • Sequence • Condition • If-Then-Else • Iterate • Repeat-Until

  14. Background • DAML Service Grounding • Defines how the service is used • Specifies communication protocol details • HTML • Java RMI, Jini • Specifies data exchange details • Data marshalling • Data format

  15. MWS • Shopping Mall for agents • Agents access web services that are services are defined with DAML-S • Mall provides categorized list of services • Categorizes by products • Categorization guarantees the type of product in the service. • Implemented with the JADE platform

  16. MWS • Services • Ontology Parser • Mall Manager • Personal Agents • Service Agents

  17. Sample service <mservice:MallService rdf:ID="Schmitt_Bookstore"> <service:presents> <mservice:MallAdvertisement rdf:ID="Schmitt_Bookstore_Advertisement"> <profile:serviceName>Schmitt Bookstore</profile:serviceName> <profile:textDescription>Schmitt Bookstore advertisement. Shop and Save</profile:textDescription> <profile:providedBy> <profile:ServiceProvider rdf:ID="Schmitt_Service_Provider"> <profile:name>Schmitt Services</profile:name> <profile:phone>999-999-9999</profile:phone> <profile:fax>123-456-789</profile:fax> <profile:email>service@schmitt.com</profile:email> <profile:physicalAddress>1000 Hilltop Circle, Baltimore, MD. 21250, USA</profile:physicalAddress> <profile:webURL>http://www.schmittbooks.com</profile:webURL> </profile:ServiceProvider> </profile:providedBy>

  18. Sample Service cont’d <mservice:MallserviceCategory> <mservice:MallProductList rdf:ID="Schmitt_Product_List"> <products:BookProducts rdf:ID="Schmitt_Books">Schmitt Books</products:BookProducts> <products:OfficeEquipments rdf:ID="Schmitt_Office">Schmitt Office </products:OfficeEquipments> </mservice:MallProductList> </mservice:MallserviceCategory> <profile:serviceType> B2C </profile:serviceType> <profile:communicationThru>DAML</profile:communicationThru> </mservice:MallAdvertisement> </service:presents> <service:describedBy> <process:ProcessModel rdf:ID="Schmitt_BuyProcess"> <service:topLevelEvent rdf:about="Schmitt_ProcessModel"/> </process:ProcessModel> </service:describedBy> </mservice:MallService>

  19. Implementation • Implemented with Java 2 programming language • JADE – Java Agent Development Framework • DAMLJessKB – DAML Jess knowledge base package • DAMLJessKB reads DAML files as a collection of triples via an RDF parser • Reads them into JESS – Java Expert Shell System

  20. Implementation • Architecture • Inter-agent communication • Exchange of data via DAML • Invoke services by composing DAML strings • DAMLQuery object • Implementation of the ontology parser • Run queries on DAML Services • Interrogates the model and grounding of services

  21. Implementation • Architecture • AgentMall object • Implements the mall manager • Subclass of jade.core.Agent • Contains a categorized directory of services • Represents the mall manager

  22. Implementation • Architecture • ServiceAgent object • Subclass of jade.core.Agent • Registers itself by accessing the mall manager’s register method • Awaits customers that wish to access its services

  23. Implementation • Architecture • PersonalAgents object • Implements the customer agents • Subclass of the jade.core.Agent • Process user’s request and determine which services it should access.

  24. Discussion • The composition of DAML services inherently include some intelligence • Using expert system libraries, agents can access a service with little communication • Errors can be made when creating DAML service objects

  25. Future Work • Agent Collaboration • Joint purchases • Service “advertises” discounts or specials for bulk purchases • Buy 1 get one free, free shipping etc. • Create mall ontologies for discounts and specials

  26. Related Work • Trading agents • Phillip Turner and Nicholas Jennings • Focuses on scalability of the “market” • Dynamic choice of collaboration methodologies

  27. Related Work • Agent Cities • Initiative to build a network of agent based services • Built on agent technology, semantic web technologies etc • Various types of applications

  28. Related Work • Semantic web technologies • Other efforts at creating ontologies for web services • WSDL • DAML web queries

  29. Conclusion • issues with global accessibility • Various implementations of web services • A few web services might become de-facto standards because of benefits

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