Web Services And Agent Oriented System Computer Science Essay

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The paper attempt to survey the existing research and development effort involving the integration of web services and agent-oriented technology using different techniques. In particular it aims at providing a representative view of current research trends by using web services efficiently with agents. This paper discuses web services, agents and some other terminologies. It discuses what approaches have been followed the suitability of these approaches and some conclusion drawn from the survey.

Introduction

Since the advent of the World Wide Web, it has been evident

that prevailing mode of human-to-machine interaction would ultimately be supplemented and extended by technology designed to support direct machine-to-machine interaction, sometimes driven by humans and sometimes in a completely autonomous mode. Recently this has begun to be manifested in the form of Web services. The W3C defines a Web service as "... a

software system designed to support interoperable machineto-

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machine interaction over a network. It has an interface

described in a machine-processable format (specifically

WSDL(Web Services Description Language)). Other systems interact with the Web service in a manner prescribed by its description using SOAP (Simple Object Access

Protocol) messages, typically conveyed using HTTP(hyper text transfer protocol) with an XML(Extensible markup language) serialization in conjunction with other Web-related standards." .

A Web service should be used when an application builder wishes to expose some reactive operation expressible as a programmatic function with or without parameters that may or may not return a response.

Similar to Web services, software agents ca also be used to encapsulate some business or application logic, but differ in that they do not simply expose functionality as methods over a fixed protocol. Rather, software agents can offer multiple services, or behaviours, that can be processed concurrently and activated by specifying goals.

Integrating Web services and software agents brings about

the immediate benefits of connecting application domains

hosting one or the other technology: A Web service should

be able to invoke an agent service and vice versa. However,

once this interconnection is established software agent concepts and technologies will help enable new and advanced

operational and usage modalities of Web services. In this perspective, identifying a means of connecting agents and Web services is the motivation and central foundation

of our work. Due to the evident technology mismatches

between Web services and software agents, including

strong vs. loose coupling and representational encodings,

different techniques have used. From the perspective of agents, Web services are simply programmatic entities that can be called upon to perform an advertised and typically unitary function. To consumers of Web services, agents can form a powerful means of indirection by masking the Web service for purposes of redirection, aggregation, integration or administration. Integration of Web services and agent-oriented system is a very active area of research and development . However, very little has been accomplished to date regarding the integration of web services and agent-based systems of Web services. Section 2 present some research on existing work done on integration of web services and agent-oriented system. Section 3 give some critical analysis on different approaches discussed for integration. Finally, Section 4 draws conclusions and highlights future work..

II. Existing Work

A.Engineering Web Service - Agent Integration

The problem as specified is to provide an automatic means

of mapping the functional and representational dependencies

associated with the invocation of agent services onto those

associated with Web services and vice versa. For this we introduces an intermediary processor into the communication

path between these service calls. The Web Service Integration Gateway Service (WSIGS) allows both agent and Web services to register with it and thereby publish their service descriptions to consumers outside their normal operational domain. The WSIGS will then intercept calls to these registered services allowing agents to invoke Web services and vice versa by transforming message encodings and creating service access endpoints.

The GatewayRegistry

This is the logical component that receives and processes

incoming directory operations, thereby controlling access to

the internal registries. ACL encoded service descriptions received from agents are stored in the internal DF( registry and automatically translated (by the Service Description Translator component) into their WSDL equivalent and stored in the internal UDDI (Universal Description, Discovery and Integration ) registry. The reverse case is also true for WSDL encoded service descriptions received from Web service owners.

GatewayRegistry Component

The ServiceDescriptionTranslator

The StubCreator

WebServiceInvocation

AgentServiceInvocation

The MessageTranslator

The Web Service Integration Gateway Service(WSIGS)

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The WSIGS has two principal modes of operation: an agent service invoking a Web service and a Web service invoking an agent service. The standard features of the WSIGS are described by the following operations:

WSIGS Initialisation

Register a Service Description

Deregistration of an existing service description.

Modification of an existing service description.

Searching for a registered service description.

Invoke an agent service from a Web service client

Invoke a Web service from an Agent

B. Mobile Web Services: A New Agent-Based Framework

We describe agent-based mobile services framework. It uses wireless portal networks and eliminates XML processing on mobile clients. It also offers dynamic service selection and rapid application development and deployment for Web service providers. The framework's overall operation is divided into three phases:

• Service development and publication. The service provider develops Web services according to its requirements. It then prepares a workflow document and submits this document with any

Web Services Description Language (WSDL).

• Service discovery. When a mobile client tries to reach a service, it sends a request to the operator. The operator creates a mobile Web service agent for the client and puts it on the network so the mobile client can communicate with its own agent. To discover the required service, the user selects a domain and a service class, and the agent

checks the service class's attributes with the service broker The user then picks one of the services in the list.

• Service execution. Using information from the service broker, the mobile Web service agent connects to the workflow engine and initiates a request to execute the selected service. The workflow engine invokes the Web service specified in the workflow Document and also workflow engine can take input from the user or present the user with output. The service provider can supply these inputs and

outputs separately

C. JADE: software framework for developing multi-agent

applications.

Integrating JADE agents with Web Services

Let's discuss the work done to integrate JADE agents with Web services and to encapsulate ''intelligence'' into JADE agents.

The possibility of invoking agent services as Web services, and the capability to realize applications as composition of agents and Web services, are very important features for the usability of the JADE software. This functionality is achieved by means of a JADE add-on

called Web Service Integration Gateway (WSIG). WSIG is able to automatically expose agent services as Web services and to convert SOAP invocations into ACL requests. JADE agents publish

their services in a registry called Directory Facilitator. WSIG listens to registrations with the Directory Facilitator and, for each registered agent service, it automatically exposes a Web Service described by a WSDL description whose operations correspond to the actions supported by the registering agent

D. Web Service Access Management for Integration with

Agent Systems

This section present a generic extension to agent platforms, called the web service gateway, for controlled web service access and usage. It supports integrated management infrastructure, for example using service level agreements, to control agent access to, and usage of, web services according to organizational policies.

MIDDLEWARE AND WEB SERVICE GATEWAY ARCHITECTURE

The web service gateway not only provides the agent application with initial access to a web service, but also acts as an intermediary for all subsequent communication between the agent application and the web service. Being a web service consumer, an agent exchanges SOAP messages with a web service port. According to the SOAP standard, these messages are carried by a SOAP transport layer. The agent therefore passes any SOAP messages it wishes to send to the port (through the middleware hosting the agent) to the web service gateway. Similarly, the web service gateway passes any SOAP messages it receives from the port to the correct agent (through the

middleware hosting the agent).

E. The IEEE FIPA Approach to Integrating Software Agents and Web Services

JADE WSIG

The JADE Web Services Integration Gateway WSIG is an open source add-on for the FIPA 2000 compliant JADE platform. It supports registration and discovery of Web services by JADE agents, registration and discovery of JADE Agents and agent services by Web service clients, translation of UDDI directory entries into DF directory entries. The WSIG Gateway Agent is responsible for (1) receiving and translating agent service registrations from the DF

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into corresponding WSDL descriptions and registering these

with the UDDI repository (2) receiving and translating

Web service operation registrations from the UDDI

repository into corresponding ACL descriptions and registering

these with the DF. (3) receiving and processing Web service

invocation requests received from JADE agents. (4) receiving and processing agent service invocation requests received from Web service clients.

DFKI Agent Messaging Framework

DFKI, Germany, has proposed a mapping between the addressing and messaging schemes in Web services and those in FIPA compliant multiagent systems. This paper briefly describes how a

particular standard from the Web services stack -the WSAddressing

standard- can be mapped to FIPA messages to achieve an interoperation between WS-compliant entities and FIPA compliant entities. The DFKI effort aims to concentrate more on determining how agents can specify their reasoning power and the services they offer.

OWL-P (Web Ontology language)

It has been recommended as a technology that will contribute to software agents' interaction with Web services and standard

Web service technologies. Components include (1) an OWL ontology to support the specification of protocols elements, (2) a rule-based representation of protocols (3) an algorithm for

combining protocols (4) an architecture that supports run time activities.

WS2JADE

Toolkit which allows JADE agents to discover Web services and use them. It addresses the following areas of agent and Web services interoperability:

• communication languages

• ontologies and service descriptions

• interaction protocols and composition languages

AgentWeb Gateway

It is an initiative toward achieving dynamic and seamless integration of FIPA compliant software agents and WSA compliant Web services. The Gateway is a middleware layer between the multi agent system and Web services facilitating integration without requiring

alteration to existing specifications.

J2ees

The central concept of J2ees is the use of agents to manage resources involved in the enactment of a distributed workflow to enable adaptability and distributability.

J2ees uses Colored Petri Nets (CPNs) to model workflows

and utilizes agents to distribute tasks in the workflow.

Analysis

The work reported in this paper is an attempt to identify

a relatively simple, yet extensible model that brings about

loosely-coupled integration of agents and Web services. As

such it is strongly influenced by and indeed evolved from,

several existing contributions to the field let us discuss these

Lyell discusses the concept of J2EE/FIPA-compliant software agent system using Colored Petri Nets. This approach identifies two key concepts that (1) agents should be able to expose their services as Web services and (2) these Web service-enabled agents should advertise using both a UDDI registry and a FIPA Directory Facilitator (DF).

WSIGS approach also addresses these issues, but without the specific use of J2EE or special "Web service agents" to expose Web services. Instead the WSIGS is intended for use with any J2*E technology platform

WSIGS is an independent set of codecs that can process and translate Agent messages and Web service calls without bringing any agents or Web services within the Gateway boundary.

In WSIGS automation can be driven by agent generators reasoning about the semantic descriptions of the Web services they are configured to compose and use

Most directly referential work relating to the WSIGS architecture is that of the Gateway Model produced by working group.

The model, intended for use by the JADE agent system, consists of two separate implementations. One WSDL2JADE is designed as a wrapper solution for converting agent sourced ACL encoded requests into the appropriate Web service operation. Second aspect allows an agent service to be published as a Web service. The implementation consists of a Web Services Agent Gateway(WSAG) and an agent Generator. In its current form, this solution is neither integrated, transparent nor automatic and has the additional drawback of requiring a degree of manual configuration.

WSIGS approach takes some of the ideas generated by this project and extends them to form a model of a transparent, automatic and extensible Gateway service.

The difference with the web service gateway and Middleware webservice Gateway is that middleware focuses on management of web service interaction. Mechanisms are presented that enforce agents to interact with web services through the middleware,so that access and usage of web sites can be managed on a sitebasis.

The potential of web service gateways for consumer side web service management has, however, not yet fully explored.

In mobile web service approach eliminating XML processing on mobile clients and SOAP-message transfer over wireless links improves performance in terms of response time and data load.

Mobile web service approach has two limitations: it gets user input from a Web page, which must be prepared beforehand, and it doesn't support background processing.

Conclusions

This survey paper discuss different approaches used to integrate web services and agent oriented system. It is anticipated that such systems will help prevent the risk of an asymptotic or divergent relationship developing between these two complementary technologies

In this paper we have presented different agent oriented web services integration strategies, introduced some existing platforms and frameworks and made an attempt to compare existing research approaches with each other.