Today’s business enterprises must deal with global competition, reduce the cost of doing business, and rapidly develop new services and products. To address these requirements enterprises must constantly reconsider and optimize the way they do business and change their information systems and applications to support evolving business processes. Workflow technology facilitates these by providing methodologies and software to support (i) business process modeling to capture business processes as workflow specifications, (ii) business process reengineering to optimize specified processes, and (iii) workflow automation to generate workflow implementations from workflow specifications. This paper provides a high-level overview of the current workflow management methodologies and software products. In addition, we discuss the infrastructure technologies that can address the limitations of current commercial workflow technology and extend the scope and mission of workflow management systems to support increased workflow automation in complex real-world environments involving heterogeneous, autonomous, and distributed information systems. In particular, we discuss how distributed object management and customized transaction management can support further advances in the commercial state of the art in this area.

Many computer-supported applications are of long duration and consist of multiple steps that are exe-cuted over possibly heterogeneous servers. Such activ-ities have weaker atomicity requirements than trans-actions. Previously, we illustrated how to organize the execution of such activities using triggers and transac-tions. In this paper, we describe an execution model in.which activities may consist recursively of steps that may be subactivities or transactions. The model defines precisely the semantics of activities: commu-nication between steps and the failure semantics of activities including compensation and exception han-dling. The model also supports querying the status of activities. We also propose an implementation of the model using recoverable queues for reliably chaining the steps according to the semantics of the model. 1

Introduction This chapter gives an overview on multilevel transactions and its generalization toward open nested transactions. The main features of these transaction models are the following: first, semantic properties of operations can be exploited to relax the isolation of concurrent transactions; second, as a consequence, atomicity is achieved by compensation rather than state-based undo; and third, subtransactions can be made persistent independently of their commit state, that is, global visibility of their updates. Advanced transaction models and new correctness criteria for transaction executions have been proposed for the following reasons (and possibly further reasons that are not mentioned here): 1. to provide better support for long-lived activities in advanced DBMS applications, 2. to relax the classical ACID paradigm, for example, provide more flexibility as to when updates are made visible to concurrent transactions, 3. to support cooperation between the members

. The computing environment in most medium-sized and large enterprises involves old main-frame based (legacy) applications and systems as well as new workstation-based distributed computing systems. The objective of the METEOR project is to support multi-system workflow applications that automate enterprise operations. This paper deals with the modeling and specification of workflows in such applications. Tasks in our heterogeneous environment can be submitted through different types of interfaces on different processing entities. We first present a computational model for workflows that captures the behavior of both transactional and nontransactional tasks of different types. We then develop two languages for specifying a workflow at different levels of abstraction: the Workflow Specification Language (WFSL) is a declarative rulebased language used to express the application-level interactions between multiple tasks, while the Task Specification Language (TSL) focuses on the issues re...

This technical report will also appear in A.K. Elmagarmid (ed.): Advanced Transaction Models for New Applications, Morgan Kaufmann Publishers, 1991. Contents 7 The ConTract Model 1

The basic transaction model has evolved over time to incorporate more complex transaction structures and to selectively modify the atomicity and isolation properties. In this chapter we discuss the application of transaction concepts to activities that involve coordinated execution of multiple tasks (possibly of different types) over different processing entities. Such applications are referred to as transactional workflows. In this chapter we discuss the specification of such workflows and the issues involved in their execution. 1 What is a Workflow? Workflows are activities involving the coordinated execution of multiple tasks performed by different processing entities. A task defines some work to be done and can be specified in a number of ways, including a textual description in a file or an email, a form, a message, or a computer program. A processing entity that performs the tasks may be a person or a software system (e.g., a mailer, an application program, a database mana...

In recent years, numerous transaction models have been proposed to address the problems posed by advanced database applications, but only a few of these models are being used in commercial products. In this paper, we make the case that such models may be too centered around databases to be useful in real environments. Advanced applications raise a variety of issues that are not addressed at all by transaction models. These same issues, however, are the basis for existing workflow systems, which are having considerable success as commercial products in spite of not having a solid theoretical foundation. We explore some of these issues and show that, in many aspects, workflow models are a superset of transaction models and have the added advantage of incorporating a variety of ideas that to this date have remained outside the scope of traditional transaction processing. 1 Introduction It is a widely accepted fact that conventional databases are unsuitable for many applications. To addr...

this paper may be "long running" or not. Other related terms used in the database literature are task flow, multitransaction activities [7], multi-system applications [1], application multiactivities, and networked applications [4]. Some related issues are also addressed in various relaxed transaction models.

Workflow technology has not yet lived up to its expectations not only because of social problems but also because of technical problems, like inflexible and rigid process specification and execution mechanisms and insufficient possibilities to handle exceptions. The aim of this paper is to present a workflow model which significantly facilitates the design and reliable management of complex business processes supported by an automatic mechanism to handle exceptions. The strength of the model is its simplicity and the application independent transaction facility (advanced control mechanism for workflow units) which guarantees reliable execution of workflow activities. 1 Introduction Among cooperative information systems, workflow management is one of the key technologies for providing efficiency and effectiveness in the office. A Workflow Management System (WFMS) is a system that completely defines, manages and executes workflow processes through the execution of software whose order o...

We propose Concurrent Transaction Logic (CT R) as the language for specifying, analyzing, and scheduling of workflows. We show that both local and global properties of workflows can be naturally represented as CT R formulas and reasoning can be done with the use of the proof theory and the semantics of this logic. We describe a transformation that leads to an efficient algorithm for scheduling workflows in the presence of global temporal constraints, which leads to decision procedures for dealing with several safety related properties such as whether every valid execution of the workflow satisfies a particular property or whether a workflow execution is consistent with some given global constraints on the ordering of events in a workflow. We also...