. Current developments show that tomorrow's information systems and applications will no longer be based on monolithic architectures that encompass all the functionality. Rather, the emerging need for distribution and quick adaptation to new requirements stemming from, e.g., virtual enterprises, demands distributed systems that can be extended dynamically to compose new services from existing software components. However, usage of mobile code introduces specific security concerns which a security system must be aware of. We present a comprehensive security architecture for extensible, distributed systems using the example of an Internet query processing service which can be extended by user-defined operators. Before an operator is actually used in queries for the first time, our OperatorCheck server validates its semantics and analyzes its quality. This is done semi-automatically using an oracle-based approach to compare a formal specification of an operator against its implementation. Further security measures are integrated into the query processing engine: during plan distribution secure communication channels are established, authentication and authorization are performed, and overload situations are avoided by admission control. During plan execution operators are guarded using Java's security model to prevent unauthorized resource access and leakage of data. The resource consumption of operators is monitored and limited with reasonable supplementary costs to avoid resource monopolization. We show that the presented security system is capable of executing arbitrary operators without risks for the executing host and the privacy and integrity of data. In the paper we will concentrate on the OperatorCheck server, as this server can itself be v...

Service portals are systems which expose a bundle of web services to the user, allowing the specification and subsequent execution of complex tasks defined over these individual services. Examples of situations where service portals would be valuable include making travel plans or purchasing a home. Service portals must be capable of converting an abstract user goal into a correct and optimal concrete execution plan, executing according to the plan, verifying the result against a user’s stated satisfaction criteria, and in the case of satisfaction failure, initiating the appropriate recovery procedures. The basic framework needed to support this functionality, from gathering the input to generating an optimal plan and executing that plan, is a prerequisite for all service portals, yet there are currently no

Process Support Systems (PSSs) are software systems supporting the modeling, enactment, monitoring, and analysis of business processes. Process automation technology can be fully exploited when predictable and repetitive processes are executed. Unfortunately, many processes are faced with the need of managing exceptional situations that may occur during their execution, and possibly even more exceptions and failures can occur when the process execution is supported by a PSS. Exceptional situations may be caused by system (hardware or software) failures, or may by related to the semantics of the business process.

This paper proposes the concept of business events as the cornerstone to web service description and coordination. First, a web service architecture is introduced as the result of an event based analysis & design phase. Then, it is advocated how the event concept can be used for semantically rich web service description. A distinction is made between two web service interfaces: a non-transactional query interface and a transactional event notification interface. Furthermore, a web service composition model is proposed, based on event broadcasting and event preconditions, instead of traditional one-to-one method invocations. The composition model is presented in a static variant and in a version with dynamic subscription. Throughout the paper, it is shown how the event based approach fits entirely within the current standard SOAP/WSDL/UDDI web services stack.

In this paper we briefly describe some current techniques and mechanisms used to ensure diversity in software applications. We then introduce and discuss an alternative approach to software diversity aiming at the reduction of widespread software attacks and faults. This approach takes advantage of the componentisation of modern software solutions and enforces diversity at the installation time by randomly selecting and deploying critical software components.

State Machines (ASMs) [3] to model business processes is being analyzed, as they present several interesting properties, namely: express functionally complete but abstract description that can be understood by a human reader, define every system features as far as it is semantically relevant for the required functionality and contain only what the logic of the problem requires for the system behavior. Furthermore, the grounding model is implemented following a refinement process, trough a hierarchy of intermediate models, and ASMs also allow structuring the system horizontally by building it from components with abstract definitions of behavior and interactions trough interfaces.

Abstract. With the sophistication and maturity of distributed component-based services and semantic web services, the idea of specification-driven service composition is becoming a reality. With relevance to this work is the workflow composition of services as they span multiple, distributed web-accessible locations. Given the dynamic nature of this domain, the autonomy and adaptation of software agents represent a possible solution for the composition and enactment of cross-organizational services. In this work, we address several aspects of such a domain. We detail design aspects of an architecture that would support this evolvable service-based workflow composition. We discuss the internal coordination and control aspects of such an architecture. A further overarching concern is the alignment of agent developmental processes with current industry standard software engineering processes.

Abstract. The autonomy and adaptation of software agents are valuable in environments that regularly change. The Internet presents such an environment, particularly with the addition of semantic web services. The connotation of distributed web services being offered across the Internet has researchers and industry personnel anticipating the seamless ability to automatically generate high-level composite services. Agents can play a measurable role in the workflow composition or “orchestration ” of these distributed services as they span multiple, distributed web-accessible locations. Though many studies have examined agent communication languages and coordination protocols based on their flexibility or completeness of information exchange, few investigations have empirical methods for evaluating the efficiency of one protocol over another. In this paper, we present several workflow-based agent coordination protocols consistent with third-party control approaches and peer-to-peer (P2P) approaches. We show the results of our experiments that evaluate these protocols in such a way that the correct approach can be determined based on specific operational conditions. These investigations are valid in the domain where agents coordinate to manage the workflow composition of distributed services. Keywords. Agent architectures, Workflow, Coordination, Linda, E-Services