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-tomarket for new services.

A mobile agent is an object which can autonomously migrate in a distributed system to perform tasks on behalf of its creator. Security issues in regard to the protection of host resources, as well as the agent themselves, raise significant obstacles in practical applications of the agent paradigm. This article describes the security architecture of Ajanta, a Java‐based system for mobile agent programming. This architecture provides mechanisms to protect server resources from malicious agents, agent data from tampering by malicious servers and communication channels during its travel, and protection of name service data and the global namespace. We present here a proxy based mechanism for secure access to server resources by agents. Using Java's class loader model and thread group mechanism, isolated execution domains are created for agents at a server. An agent can contain three kinds of protected objects: read‐only objects whose tampering can be detected, encrypted objects for specific servers, and a secure append‐only log of objects. A generic authentication protocol is used for all client–server interactions when protection is required. Using this mechanism, the security model of Ajanta enforces protection of namespaces, and secure execution of control primitives such as agent recall or abort. Ajanta also supports communication between agents using RMI, which can be controlled if required by the servers' security policies. Copyright © 2001 John Wiley & Sons, Ltd.

This paper describes an extended role-based access control (RBAC) model, which makes RBAC sensitive to the context of an attempted operation. Traditional RBAC does not specify whether the permissions associated with a role enable access to a particular object, or to some subset of objects belonging to a class. We extend the model by introducing the notions of role context and context filters. Context filters are Boolean expressions based on the context of the user attempting the operation, as well as the context of the object upon which the operation is attempted. By supplying context filters during the definition of a role, a security administrator can easily limit the applicability of users' role memberships to particular subsets of the target objects. We also describe our implementation of the model in a web-services platform, to illustrate how this technique is particularly valuable when the data is hierarchically structured.

We describe the mobile agent paradigm which is becoming increasingly popular for network-centric programming, and compare it with earlier paradigms for distributed computing from which it has evolved. The design of mobile agent systems requires the resolution of several system-level issues, such as the provision of code mobility, object naming, portability, scalability, and a range of security issues that go hand-in-hand with mobile code. Agent programming requires suitable languages and programming models that can support code mobility, and runtime systems that provide some fundamental primitives for the creation, migration and management of agents. We discuss these requirements and describe several mobile agent systems that illustrate di erent approaches taken by designers to address the problems.

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