. Today's workflow management systems (WFMSs) are only applicable in a secure and safe manner if the business process (BP) to be supported is well-structured and there is no need for ad hoc deviations at runtime. As only few BPs are static in this sense, this significantly limits the applicability of current workflow (WF) technology. On the other hand, to support dynamic deviations from premodeled task sequences must not mean that the responsibility for the avoidance of consistency problems and run-time errors is now completely shifted to the (naive) end user. In this paper we present a formal foundation for the support of dynamic structural changes of running WF instances. Based upon a formal WF model (ADEPT), we define a complete and minimal set of change operations (ADEPT flex ) that support users in modifying the structure of a running WF, while maintaining its (structural) correctness and consistency. The correctness properties defined by ADEPT are used to determine whether a spec...

There is an increasing interest in changing information systems to support business processes in a more direct way. This means to actively deliver tasks to be performed to the right persons at the right point in time with the necessary information and application functions needed for performing this task. Process-oriented workflow technology is a very interesting candidate to achieve this goal. In fact, many companies have already started to implement information systems based on this kind of technology. Hence the important question arises, how far do we get using this technology. Is the functionality provided powerful enough to support a wide range of application scenarios or is it only suitable for rather simple applications? And, if the latter is the case, are the missing functions of the "just to do" type or are more fundamental issues addressed? The paper uses the clinical application scenario to explain, to motivate, and to elaborate the functionality needed to adequately support...

Workflow management systems (WFMS) that are geared for the orchestration of business processes across multiple organizations are complex distributed systems: they consist of multiple workflow engines, application servers, and communication middleware servers such as ORBs, where each of these server types can be replicated on multiple computers for scalability and availability. Finding an appropriate system configuration with guaranteed application-specific quality of service in terms of throughput, response time, and tolerable downtime is a major challenge for human system administrators. This paper presents a tool that largely automates the task of configuring a distributed WFMS. Based on a suite of mathematical models, the tool derives the necessary degrees of replication for the various server types in order to meet specified goals for performance and availability as well as "performability " when service is degraded due to outages of individual servers. The paper describes the configuration tool, with emphasis on how to capture the load behavior of workflows in a realistic manner. We also present extensive experiments that evaluate the accuracy of the tool's underlying models and demonstrate the practical feasibility of automating the task of configuring a distributed WFMS. The experiments use a detailed simulation which in turn has been validated through measurements with the Mentor-lite prototype system.

Trends towards increased business process automation, e-commerce, and e-business have led to increasing interest in the field of workflow management. In this paper, we provide a perspective on the state of research in workflow management systems, and discuss possible future research directions in this area, with a particular emphasis on workflow systems in integrating interorganizational processes and enabling e-commerce solutions.

The impressive advances in global networking and information technology provide great opportunities for all kinds of ubiquitous information services, ranging from digital libraries and information discovery to virtual-enterprise workflows and electronic commerce. However, many of these services too often exhibit rather poor quality and are thus unsuitable for mission-critical applications. In this paper I would like to encourage more intensive research efforts towards service quality guarantees, the ultimate goal being the ability to construct and deploy truly dependable systems with provable correctness, continuous availability, and predictable performance. The paper aims to sort out some of the issues towards these elusive goals, mainly by discussing a case study on workflow management. I will point out various assets that can be leveraged, most notably, from database and TP technology and also mathematical modeling and reasoning, and I will outline some research directions that I wo...

Web services are increasingly attracting attention for their ability to pro-vide standard interfaces to heterogeneous distributed services. Through these standard interfaces, it is possible to compose more complex services out of basic ones. In this paper, we tackle the problem of visual service compo-sition and the efficient and scalable execution of the resulting composite services. Our efforts revolve around the JOpera system, which combines a visual programming environment for Web services with a flexible execution engine capable of interacting with Web services through the SOAP protocol, described with WSDL, and registered with an UDDI registry. In the paper we describe the syntax of the JOpera Visual Composition Language (JVCL), its implementation, and how to provide different QoS levels in the execution of composite services.

Abstract. For enterprise-wide and cross-enterprise workflow (WF) applications, the load of the WF servers and the amount of communication in the subnets may become a bottleneck. This paper shows how a distributed WF control can be realized in a way that the load of the components at run time is minimized. For that purpose, the control of a WF instance may migrate from one WF server to another. The WF servers are assigned to the WF activities in a way that minimizes the communication load. The server assignments are determined at build time by analyzing the WF model with respect to the actor assignments. As these actor assignments may depend on preceding activities, static server assignments are not always reasonable. Hence, so-called variable server assignment expressions are introduced, which allow dynamic server assignment without expensive run time analyses. 1

The paper discusses important challenges and research issues for adaptive workflow management systems (WfMS), especially if they shall be applied to enterprise-wide applications. It shows that an adaptive WfMS must provide support for different kinds of (dynamic) workflow (WF) changes in order to be applicable to a broader spectrum of processes. In this context, both, requirements for WF schema evolution and issues related to ad-hoc changes of individual WF instances are discussed. A particulary interesting aspect, which is described in more detail, is how to combine such dynamic changes with a distributed execution of workflows, taking into account performance issues. For enterprise-wide and cross-enterprise workflows, the distributed execution of workflows may be attractive due to several reasons. 1 Introduction Workflow Management Systems (WfMS) offer a promising technology that has the potential to change the implementation of enterprise-wide and cross-enterprise application syst...

Software development nowadays involves several levels of abstraction: starting from the programming of single objects, to their combination into components, to their publication as services and the overall architecture linking elements at each level. As a result, software engineering is dealing with a wider range of artifacts and concepts (i.e., in the context of this paper: services and business processes) than ever before. In this paper we explore the importance of having an adequate engine for executing business processes written as compositions of Web services. The paper shows that, independently of the composition language used, the overall scalability of the system is determined by how the run time engine treats the process execution. This is particularly relevant at the service level because publishing a process through a Web service interface makes it accessible to an unpredictable and potentially very large number of clients. As a consequence, the process developer is confronted with the difficult question of resource provisioning. Determining the optimal configuration of the distributed engine that runs the process becomes sensitive

Introduction and Background In the ADEPT 1 project [ADEPT] we are looking at different facets of advanced process-oriented information systems in conjunction with each other: Component-based application development, exception handling and flexibility issues, dynamic workflow changes, temporal aspects, workflow evolution, inter-workflow dependencies, man-machine interfaces, scalability, and WfMS architectures and implementation. The roots of the ADEPT project go back into the year 1992, when the interdisciplinary research project "Open Clinical Information and Database System for the Integration of Autonomous Subsystems" (OKIS, 1992-94) started. The intensive discussions we had with the medical personnel and the investigations performed within the OKIS project have made clear to us that "passive", data-centric information systems alone are by far not sufficient to solve the pressing problems found in most clinical application areas. Being conf