Neeran M. Karnik

Design issues in mobile agent programming systems

The article discusses system-level issues and agent programming requirements that arise in the design of mobile agent systems. The authors describe several mobile agent systems to illustrate different approaches designers have taken in addressing these challenges. The following areas are discussed: agent mobility, naming, security issues, privacy and integrity, authentication, authorization and access control, metering and charging mechanisms, programming primitives, agent communication and synchronization primitives, agent monitoring and control primitives, and fault tolerance primitives.

A service creation environment based on end to end composition of Web services

The demand for quickly delivering new applications is increasingly becoming a business imperative today. Application development is often done in an ad hoc manner, without standard frameworks or libraries, thus resulting in poor reuse of software assets. Web services have received much interest in industry due to their potential in facilitating seamless business-to-business or enterprise application integration. A web services composition tool can help automate the process, from creating business process functionality, to developing executable workflows, to deploying them on an execution environment. However, we find that the main approaches taken thus far to standardize and compose web services are piecemeal and insufficient. The business world has adopted a (distributed) programming approach in which web service instances are described using WSDL, composed into flows with a language like BPEL and invoked with the SOAP protocol. Academia has propounded the AI approach of formally representing web service capabilities in ontologies, and reasoning about their composition using goal-oriented inferencing techniques from planning. We present the first integrated work in composing web services end to end from specification to deployment by synergistically combining the strengths of the above approaches. We describe a prototype service creation environment along with a use-case scenario, and demonstrate how it can significantly speed up the time-to-market for new services.

Synthy: A system for end to end composition of web services

The demand for quickly delivering new applications is increasingly becoming a business imperative today. However, application development is often done in an ad hoc manner resulting in poor reuse of software assets and longer time-to-delivery. Web services have received much interest due to their potential in facilitating seamless business-to-business or enterprise application integration. A web service composition system can help automate the process, from specifying business process functionalities, to developing executable workflows that capture non-functional (e.g. Quality of Service (QoS)) requirements, to deploying them on a runtime infrastructure. Intuitively, web services can be viewed as software components and the process of web service composition similar to software synthesis. In addition, service composition needs to address the build-time and runtime issues of the integrated application, thereby making it a more challenging and practical problem than software synthesis. However, current solutions based on business web services (using WSDL, BPEL, SOAP, etc.) or semantic web services (using ontologies, goal-directed reasoning, etc.) are both piecemeal and insufficient. We formulate the web service composition problem and describe the first integrated system for composing web services end to end, i.e., from specification to deployment. The proposed solution is based on a novel two-staged composition approach that addresses the information modeling aspects of web services, provides support for contextual information while composing services, employs efficient decoupling of functional and non-functional requirements, and leads to improved scalability and failure handling. We also present Synthy, a prototype of the service composition system, and demonstrate its effectiveness with the help of an application scenario from the telecom domain.

Mobile agent programming in Ajanta

The paper gives an overview of Ajanta, a Java based system for mobile agent programming. We outline the Ajanta architecture, and discuss the basic elements that comprise an agent based application. Ajantas programming environment is defined in terms of a set of primitive operations for agent creation, dispatch, migration and remote control. Agents can access server resources using a proxy based access control mechanism. We describe a scheme for agent migration based on the composition of some basic migration patterns which incorporate exception handling mechanisms. Finally, we present two agent based distributed applications implemented using the Ajanta system. One is a middleware which supports file sharing over the Internet and the other is a distributed calendar manager.

Design of the Ajanta system for mobile agent programming

Abstract We describe the architecture and programming environment of Ajanta, a Java-based system for programming applications using mobile agents over the Internet. Agents are mobile objects which are hosted by servers on the network. Ajanta provides primitives for creating and dispatching agents, securely controlling agents at remote sites, and transferring agents from one server to another. For secure access to server resources by visiting agents, a proxy-based access control mechanism is used. The Ajanta design includes mechanisms to protect an agents state and prevent misuse of its credentials. We describe the use of migration patterns for programming an agents travel path. A pattern encapsulates the abstract notion of agent mobility. Pattern composition allows one to build complex travel plans using some basic migration patterns. Finally, we present agent-based distributed applications implemented using the Ajanta system to demonstrate Ajantas functional capabilities. These include a distributed calendar management system, a middleware for sharing files over the Internet, an agent-based middleware for distributed collaborations, and an agent-based network monitoring system.

SYNCHRONIZATION ANALYSIS FOR DECENTRALIZING COMPOSITE WEB SERVICES

Web Services are emerging as the standard mechanism for making information and software available programmatically via the Internet, and as building blocks for applications. A composite web service may be built using multiple component web services. Once its specification has been developed, the composite service may be orchestrated either using a centralized engine or in a decentralized fashion. Decentralized orchestration brings performance benefits, and improves scalability and concurrency. Dynamic binding coupled with decentralized orchestration adds high availability and fault tolerance to the system. However in such systems, the coordination between components needs to be carefully designed to ensure correct execution of the composite and to limit the synchronization overheads. In this paper, we categorize different forms of concurrency and provide an algorithm to identify these forms in a composite service specification. We explore different mechanisms for transferring data between the components in the presence of different forms of concurrency. Then we experimentally evaluate the efficiency and scalability of each mechanism. We also analyze the coordination requirements of a decentralized orchestration in the presence of dynamic binding and fault propagation.

Experiences and future challenges in mobile agent programming

Abstract The current research in mobile agent systems has demonstrated the utility of this paradigm in building a wide range of distributed applications and systems. In this paper, we present the promising areas for mobile agent based applications. These range from network management, to personal assistants over the Internet, to distributed collaborations. There are many mobile agent programming platforms available today. A large cross-section of these are based on Java. The design of a mobile agent programming platform requires addressing several important problems. In this paper, we discuss these design issues and show how some of the contemporary mobile agent systems have addressed these in their designs. We focus particularly on the Ajanta system, which is a good representative of modern Java-based agent programming platforms. We present here two applications developed using Ajanta, and we discuss the future challenges for research in this field.

Synchronization analysis for decentralizing composite Web services

Web Services are emerging as the standard mechanism for making information and software available programmatically via the Internet, and as building blocks for applications. A composite web service may be built using multiple component web services. Once its specification has been developed, the composite service may be orchestrated either using a centralized engine or in a decentralized fashion. Decentralized orchestration improves scalability and concurrency. Dynamic binding coupled with decentralized orchestration adds high availability and fault tolerance to the system. In this paper, we categorize different forms of concurrency and provide an algorithm to identify these forms in a composite service specification. We also consider the impact of dynamic binding and faults on synchronization constructs.

Metering and accounting for composite e-services

Software services are emerging as the dominant component technology for distributed applications. Using standardized interfaces, clients can remotely access functionality or resources offered by service providers. In e-commerce applications, often such services will be fee-based. Usage metering and Accounting thus form important components of an e-services infrastructure. The metering and accounting problem takes on added complexity with composite e-services - higher-level services built using simpler underlying services, each of which may be independently owned. We present an architecture for the metering and accounting of composite service usage.

Protected resource access for mobile agent-based distributed computing

This paper describes the mobile agent paradigm for distributed computing, and outlines the security-related issues encountered in supporting it. One of the major requirements is the provision of access control mechanisms for server resources. Several possible designs are discussed, and one such proxy-based design, which we have developed in conjunction with the Ajanta mobile agent system, is described in detail. Extensions of this mechanism which allow accounting of usage and selective revocation of access privileges are discussed. The Java security model is also described, since the security of the proxy mechanism depends on it.