Mohan Kamath

Bio: Mohan Kamath is an academic researcher from University of Massachusetts Amherst. The author has contributed to research in topics: Workflow management system & Workflow engine. The author has an hindex of 11, co-authored 13 publications receiving 998 citations.

Advanced transaction models in workflow contexts

Abstract: 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 have so far remained outside the scope of traditional transaction processing.

Exotica/FMQM: A Persistent Message-Based Architecture for Distributed Workflow Management

Abstract: In the past few years there has been an increasing interest in workflow applications as a way of supporting complex business processes in modern corporations. Given the nature of the environment and the technology involved, workflow applications are inherently distributed and pose many interesting challenges to the system designer. In most cases, a client/server architecture is used in which knowledge about the processes being executed is centralized in one node to facilitate monitoring, auditing, and to simplify synchronization. In this paper, we explore a novel distributed architecture, Exotica/FMQM, for workflow systems in which the need for such a centralized database is eliminated. Instead, we use persistent messages as the means to store the information relevant to the execution of a business process. Our approach is to completely distribute the execution of a process so individual nodes are independent. The advantages of this approach are increased resilience to failures and greater scalability and flexibility of the system configuration.

Continuous Media Sharing in Multimedia Database Systems

Abstract: The timeliness and synchronization requirements of multimedia data demand e&ient buffer management and disk access schemes for multimedia database systems. The data rates involved are very high and despite the developmenl of eficient storage and retrieval strategies, disk I/O is a potential bottleneck, which limits the number of concurrent sessions supported by a system. This calls for more eficient use of data that has already been brought into the buffer. We introduce the notion of continuous media caching, which is a simple and novel technique where data that have been played back by a user are preserved in a controlled fashion for use by subsequent users requesting the same data. We present heuristics to determine when continuous media sharing is beneficial and describe the bufler management algorithms. Simulation studies indicate that our technique substantially improves the performance of multimedia database applications where data sharing is possible.

Providing High Availability in Very Large Worklflow Management Systems

Abstract: Workflow management systems (WFMS) support the modeling, coordinated execution and monitoring of business processes within an organization. In particular, very large workflow management systems are used in organizations with several thousand users, hundreds of thousands of process instances, and several thousand sites, all distributed over wide geographic areas. In these environments, failure of the WFMS or the underlying workflow database which stores the meta-information about the processes is not tolerable. This paper addresses the problem of providing high availability in workflow management systems by proposing a backup technique which ensures that execution of a process instance can be resumed at any point in time in the event of a failure. An essential characteristic of our backup scheme is that it allows the user to define different availability levels, reducing the cost of maintaining backups. The backup scheme is implemented using the workflow semantics, which we believe will (i) make it independent of the underlying workflow database, thus permitting the use of heterogeneous databases as primary and backup, (ii) reduce overheads, especially when compared to backup schemes provided by database systems.

Exotica/FMDC: Handling Disconnected Clients in a Workflow Management System.

Abstract: Workkow Management Systems (WFMS) are a rst generation of products that attempt to manage the execution of business processes by large numbers of users distributed over a wide area and using heterogeneous resources. They are a very promising venue for collab-orative systems but, in most cases, the autonomy of the users is greatly restricted due to architectural and design considerations. This is a severe restriction, especially when considering the emergence of mobile computing , and the increase in use of laptops and small computers which are connected to a network only occasionally. In this paper, we discuss how disconnected workkow clients can be supported while preserving the correctness of the overall execution and allowing coordinated interactions between the diierent users. Disconnected client support provides a great deal of ex-ibility in the usability of a WFMS and enhances the system's resilience to failures.

Modeling Quality of Service for Workflows and Web Service Processes

Abstract: Workflow management systems (WfMSs) have been used to support various types of business processes for more than a decade now. In workflows for e-commerce and Web service applications, suppliers and customers define a binding agreement or contract between the two parties, specifying Quality of Service (QoS) items such as products or services to be delivered, deadlines, quality of products, and cost of services. The management of QoS metrics directly impacts the success of organizations participating in e-commerce. Therefore, when services or products are created or managed using workflows, the underlying workflow system must accept the specifications and be able to estimate, monitor, and control the QoS rendered to customers. In this paper, we present a predictive QoS model that makes it possible to compute the quality of service for workflows automatically based on atomic task QoS attributes. To this end, we present a model that specifies QoS and describe an algorithm and a simulation system in order to compute, analyze and monitor workflow QoS metrics.

YAWL: yet another workflow language

Abstract: Based on a rigorous analysis of existing workflow management systems and workflow languages, a new workflow language is proposed: yet another workflow language (YAWL). To identify the differences between the various languages, we have collected a fairly complete set of workflow patterns. Based on these patterns we have evaluated several workflow products and detected considerable differences in their ability to capture control flows for non-trivial workflow processes. Languages based on Petri nets perform better when it comes to state-based workflow patterns. However, some patterns (e.g. involving multiple instances, complex synchronisations or non-local withdrawals) are not easy to map onto (high-level) Petri nets. This inspired us to develop a new language by taking Petri nets as a starting point and adding mechanisms to allow for a more direct and intuitive support of the workflow patterns identified. This paper motivates the need for such a language, specifies the semantics of the language, and shows that soundness can be verified in a compositional way. Although YAWL is intended as a complete workflow language, the focus of this paper is limited to the control-flow perspective.

Adept _flex —Supporting Dynamic Changes of Workflows Without Losing Control

Abstract: Today‘s workflow management systems (WFMS_s) 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 run-time. 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 specific change can be applied to a given WF instance or not. If these properties are violated, the change is either rejected or the correctness must be restored by handling the exceptions resulting from the change. We discuss basic issues with respect to the management of changes and the undoing of temporary changes at the instance level. Recently we have started the design and implementation of ADEPT_workflow, the ADEPT workflow engine, which will make use of the change facilities presented in this paper.

Mining process models from workflow logs

Abstract: Modern enterprises increasingly use the workflow paradigm to prescribe how business processes should be performed. Processes are typically modeled as annotated activity graphs. We present an approach for a system that constructs process models from logs of past, unstructured executions of the given process. The graph so produced conforms to the dependencies and put executions present in the log. By providing models that capture the previous executions of the process, this technique allows easier introduction of a workflow system and evaluation and evolution of existing process models. We also present results from applying the algorithm to synthetic data sets as well as process logs obtained from an IBM Flowmark installation.