With the advent of Grid and application technologies, scientists and engineers are building more and more complex applications to manage and process large data sets, and execute scientific experiments on distributed resources. Such application scenarios require means for composing and executing complex workflows. Therefore, many efforts have been made towards the development of workflow management systems for Grid computing. In this paper, we propose a taxonomy that characterizes and classifies various approaches for building and executing workflows on Grids. We also survey several representative Grid workflow systems developed by various projects world-wide to demonstrate the comprehensiveness of the taxonomy. The taxonomy not only highlights the design and engineering similarities and differences of state-of-the-art in Grid workflow systems, but also identifies the areas that need further research.

The emerging paradigm of electronic services promises to bring to distributed computation and services the flexibility that the web has brought to the sharing of documents. An understanding of fundamental properties of e-service composition is required in order to take full advantage of the paradigm. This paper examines proposals and standards for e-services from the perspectives of XML, data management, workflow, and process models. Key areas for study are identified, including behavioral service signatures, verification and synthesis techniques for composite services, analysis of service data manipulation commands, and XML analysis applied to service specifications. We give a sample of the relevant results and techniques in each of these areas.

Business Process Management (BPM) includes methods, techniques, and tools to support the design, enactment, management, and analysis of operational business processes. It can be considered as an extension of classical Workflow Management (WFM) systems and approaches.

The recently released Business Process Execution Language for Web Services (BPEL4WS) is said to combine the best of other standards for web services composition such as WSFL from IBM and XLANG of Microsoft. BPEL4WS allows for a mixture of block structured and graph structured process models thus making the language expressive at the price of being complex. Although BPEL4WS is not such a bad proposal by itself, it is remarkable how much attention this standard receives while the more fundamental issues and problems such as semantics, expressiveness, and adequacy do not get the attention they deserve. Having a standard is a very good idea. However, there are too many of them and most of them die before becoming mature. A simple indicator of this development is the increasing length of acronyms: PDL, XPDL, BPSS, EDOC, BPML, WSDL, WSCI, ebXML, and BPEL4WS are just some of the acronyms referring to various standards in the domain. Another problem is that these languages typically have no clearly defined semantics. The only way to overcome these problems is to critically evaluate the so-called standards for web services composition, i.e., Don’t go with the flow!

We describe a tool that supports verification of workflow models specified in UML activity graphs. The tool translates an activity graph into an input format for a model checker according to a semantics we published earlier. With the model checker arbitrary propositional requirements can be checked against the input model. If a requirement fails to hold an error trace is returned by the model checker. The tool automatically translates such an error trace into an activity graph trace by high-lighting a corresponding path in the activity graph. One of the problems that is dealt with is that model checkers require a finite state space whereas workflow models in general have an infinite state space. Another problem is that strong fairness is necessary to obtain realistic results. Only model checkers that use a special model checking algorithm for strong fairness are suitable for verifying workflow models. We analyse the structure of the state space. We illustrate our approach with some example verifications.

In the last decade, workflow technology has become one of the building blocks for realizing enterprise information systems. Unfortunately, the application of contemporary workflow management systems is limited to well-defined and wellcontrolled environments. In practice, workflow technology often fails because of limited flexibility. We advocate a paradigm shift to overcome this problem: Workflows should not be driven by pre-specified control-flows but by the products they generate. This paper presents the software package FLOWer which fully supports this paradigm shift. Categories and Subject Descriptors H.4.1 [Information Systems Applications]: Office Automation - Workflow management. General Terms Management, Design, Human Factors, Languages, Theory, Verification. Keywords Workflow management, case handling, workflow management systems, product-driven design, FLOWer. 1.

Recently, Nüttgens and Rump proposed a formal semantics for Event driven Process Chains (EPCs), which should be fully compliant with the informal semantics of EPCs. But, their semantics has a severe flaw. This flaw reveals that there is a fundamental problem with the informal semantics of EPCs. Here, we pin-point the cause of this problem, we show that there is no sound formal semantics for EPCs that is fully compliant with the informal semantics, and we discuss some consequences.

Organizations increasingly define many business processes as projects executed by “virtual (project) teams”, where team members from within an organization cooperate with “outside ” experts. Virtual teams require and enable people to collaborate across geographical distance and professional (organizational) boundaries and have a somewhat stable team configuration with roles and responsibilities assigned to team members. Different people, coming from different organizations will have their own preferences and experiences and cannot be expected to undergo a long learning cycle before participating in team activities. Thus, efficient communication, coordination, and process-aware collaboration remain a fundamental challenge. In this paper we discuss the current shortcomings of approaches in the light of virtual teamwork (mainly Workflow, Groupware, and Project Management) based on models and underlying metaphors. Furthermore, we present a novel approach for virtual teamwork by tightly integrating all associations between processes, artifacts, and resources. In this paper we analyze (a) the relevant criteria for process-aware collaboration system metaphors, (b) coordination models and constructs for organizational structures of virtual teams as well as for ad hoc and collaborative processes composed out of tasks, and (c) architectural considerations as well as design and implementation issues for an integrated process-aware collaboration system for virtual teams on the Internet.

We introduce COWS (Calculus for Orchestration of Web Services), a new foundational language for SOC whose design has been influenced by WS-BPEL, the de facto standard language for orchestration of web services. COWS combines in an original way a number of ingredients borrowed from well-known process calculi, e.g. asynchronous communication, polyadic synchroniza-tion, pattern matching, protection, delimited receiving and killing activities, while resulting different from any of them. Several examples illustrates COWS peculiarities and show its expressiveness both for modelling imperative and orchestration constructs, e.g. web services, flow graphs, fault and compensation handlers, and for encoding other process and orchestration languages.

Abstract. Orc is a new language for task orchestration, a form of concurrent programming with applications in workflow, business process management, and web service orchestration. Orc provides constructs to orchestrate the concurrent invocation of services – while managing timeouts, priorities, and failure of services or communication. In this paper, we show a trace-based semantic model for Orc, which induces a congruence on Orc programs and facilitates reasoning about them. Despite the simplicity of the language and its semantic model, Orc is able to express a variety of useful orchestration tasks. 1