Computer Science Department, University of Pittsburgh, Pittsburgh, PA 15260, USA

This special issue focuses on current efforts to represent and support workflows that integrate information systems and human resources within a business or manufacturing enterprise. Workflows may also be viewed as an emerging computational paradigm for effective structuring of cooperative applications involving human users and access to diverse data types not necessarily maintained by traditional database management systems.

A workflow is an automated organizational process (also called business process) which consists of a set of activities or tasks that need to be executed in a particular controlled order over a combination of heterogeneous database systems and legacy systems. Within workflows, tasks are performed cooperatively by either human or computational agents in accordance with their roles in the organizational hierarchy.

The challenge in facilitating the implementation of workflows lies in developing efficient workflow management systems. A workflow management system (also called workflow server, workflow engine or workflow enactment system) provides the necessary interfaces for coordination and communication among human and computational agents to execute the tasks involved in a workflow and controls the execution orderings of tasks as well as the flow of data that these tasks manipulate. That is, the workflow management system is responsible for correctly and reliably supporting the specification, execution, and monitoring of workflows. The six papers selected (out of the twenty-seven submitted for this special issue of Distributed Systems Engineering) address different aspects of these three functional components of a workflow management system.

In the first paper, `Correctness issues in workflow management', Kamath and Ramamritham discuss the important issue of correctness in workflow management that constitutes a prerequisite for the use of workflows in the automation of the critical organizational/business processes. In particular, this paper examines the issues of execution atomicity and failure atomicity, differentiating between correctness requirements of system failures and logical failures, and surveys techniques that can be used to ensure data consistency in workflow management systems.

While the first paper is concerned with correctness assuming transactional workflows in which selective transactional properties are associated with individual tasks or the entire workflow, the second paper, `Scheduling workflows by enforcing intertask dependencies' by Attie et al, assumes that the tasks can be either transactions or other activities involving legacy systems. This second paper describes the modelling and specification of conditions involving events and dependencies among tasks within a workflow using temporal logic and finite state automata. It also presents a scheduling algorithm that enforces all stated dependencies by executing at any given time only those events that are allowed by all the dependency automata and in an order as specified by the dependencies.

In any system with decentralized control, there is a need to effectively cope with the tension that exists between autonomy and consistency requirements. In `A three-level atomicity model for decentralized workflow management systems', Ben-Shaul and Heineman focus on the specific requirement of enforcing failure atomicity in decentralized, autonomous and interacting workflow management systems. Their paper describes a model in which each workflow manager must be able to specify the sequence of tasks that comprise an atomic unit for the purposes of correctness, and the degrees of local and global atomicity for the purpose of cooperation with other workflow managers. The paper also discusses a realization of this model in which treaties and summits provide an agreement mechanism, while underlying transaction managers are responsible for maintaining failure atomicity.

The fourth and fifth papers are experience papers describing a workflow management system and a large scale workflow application, respectively. Schill and Mittasch, in `Workflow management systems on top of OSF DCE and OMG CORBA', describe a decentralized workflow management system and discuss its implementation using two standardized middleware platforms, namely, OSF DCE and OMG CORBA. The system supports a new approach to workflow management, introducing several new concepts such as data type management for integrating various types of data and quality of service for various services provided by servers.

A problem common to both database applications and workflows is the handling of missing and incomplete information. This is particularly pervasive in an `electronic market' with a huge number of retail outlets producing and exchanging volumes of data, the application discussed in `Information flow in the DAMA project beyond database managers: information flow managers'. Motivated by the need for a method that allows a task to proceed in a timely manner if not all data produced by other tasks are available by its deadline, Russell et al propose an architectural framework and a language that can be used to detect, approximate and, later on, to adjust missing data if necessary.

The final paper, `The evolution towards flexible workflow systems' by Nutt, is complementary to the other papers and is a survey of issues and of work related to both workflow and computer supported collaborative work (CSCW) areas. In particular, the paper provides a model and a categorization of the dimensions which workflow management and CSCW systems share.

Besides summarizing the recent advancements towards efficient workflow management, the papers in this special issue suggest areas open to investigation and it is our hope that they will also provide the stimulus for further research and development in the area of workflow management systems.