Sena Nural Arpinar

Workflow history management

A workflow history manager maintains the information essential for workflow monitoring and data mining as well as for recovery and authorization purposes.Certain characteristics of workflow systems like the necessity to run these systems on heterogeneous, autonomous and distributed environments and the nature of data, prevent history management in workflows to be handled by the classical data management techniques like distributed DBMSs. We further demonstrate that multi-database query processing techniques are also not appropriate for the problem at hand.In this paper, we describe history management, i.e., the structure of the history and querying of the history, in a fully distributed workflow architecture realized in conformance with Object Management Architecture (OMA) of OMG. By fully distributed architecture we mean that the scheduler of the workflow system is distributed and in accordance with this, the history objects related with activities are stored on data repositories (like DBMSs, files) available at the sites involved. We describe the structure of the history objects determined according to the nature of the data and the processing needs, and the possible query processing strategies on these objects using the Object Query Service of OMG. We then present the comparison of these strategies according to a cost model developed.

Formalization of Workflows and Correctness Issues in the Presence of Concurrency

In this paper, main components of a workflow system that are relevant to the correctness in the presence of concurrency are formalized based on set theory and graph theory. The formalization which constitutes the theoretical basis of the correctness criterion provided can be summarized as follows:-Activities of a workflow are represented through a notation based on set theory to make it possible to formalize the conceptual grouping of activities.-Control-flow is represented as a special graph based on this set definition, and it includes serial composition, parallel composition, conditional branching, and nesting of individual activities and conceptual activities themselves.-Data-flow is represented as a directed acyclic graph in conformance with the control-flow graph.The formalization of correctness of concurrently executing workflow instances is based on this framework by defining two categories of constraints on the workflow environment with which the workflow instances and their activities interact. These categories are:-Basic constraints that specify the correct states of a workflow environment.-Inter-activity constraints that define the semantic dependencies among activities such as an activity requiring the validity of a constraint that is set or verified by a preceding activity.Basic constraints graph and inter-activity constraints graph which are in conformance with the control-flow and data-flow graphs are then defined to represent these constraints. These graphs are used in formalizing the intervals among activities where an inter-activity constraint should be maintained and the intervals where a basic constraint remains invalid.A correctness criterion is defined for an interleaved execution of workflow instances using the constraints graphs. A concurrency control mechanism, namely Constraint Based Concurrency Control technique is developed based on the correctness criterion. The performance analysis shows the superiority of the proposed technique. Other possible approaches to the problem are also presented.

Design and Implementation of a Distributed Workflow Management System: METUFlow

Workflows are activities involving the coordinated execution of multiple tasks performed by different processing entities, mostly in distributed heterogeneous environments which are very common in enterprises of even moderate complexity. Centralized workflow systems fall short to meet the demands of such environments.

An open electronic marketplace through agent-based workflows: MOPPET

Abstract.We propose an electronic marketplace architecture, called MOPPET, where the commerce processes in the marketplace are modeled as adaptable agent-based workflows. The higher level of abstraction provided by the workflow technology makes the customization of electronic commerce processes for different users possible. Agent-based implementation, on the other hand, provides for a highly reusable component-based workflow architecture as well as negotiation ability and the capability to adapt to dynamic changes in the environment. Agent communication is handled through Knowledge Query and Manipulation Language (KQML). A workflow-based architecture also makes it possible for complete modeling of electronic commerce processes by allowing involved parties to be able to invoke already existing applications or to define new tasks and to re-structure the control and data flow among the tasks to create custom built process definitions. In the proposed architecture all data exchanges are realized through Extensible Markup Language (XML) providing uniformity, simplicity and a highly open and interoperable architecture. Metadata of activities are expressed through Resource Description Framework (RDF). Common Business Library (CBL) is used for achieving interoperability across business domains and domain specific Document Type Definitions (DTDs) are used for vertical industries. We provide our own specifications for missing DTDs to be replaced by the original specifications when they become available.

A workflow-based electronic marketplace on the Web

In this paper, we describe an architecture for an open marketplace exploiting the workflow technology and the currently emerging data exchange and metadata representation standards on the Web. In this market architecture electronic commerce is realized through the adaptable workflow templates provided by the marketplace to its users. Having workflow templates for electronic commerce processes results in a component-based architecture where components can be agents (both buying and selling) as well as existing applications invoked by the workflows. Other advantages provided by the workflow technology are forward recovery, detailed logging of the processes through workflow history manager and being able to specify data and control flow among the workflow components. In the architecture proposed, the resources expose their metadata using Resource Description Framework (RDF) to be accessed by the resource discovery agents and their content through Extensible Markup Language (XML) to be accessed by the selling agents by using Document Object Model (DOM). The common set of Document Type Definitions (DTDs) are used to eliminate the need for an ontology. The marketplace contains an Intelligent Directory Service (IDS) which makes it possible for agents to find out about each other through a match making mechanism. References to the related Document Type Definitions (DTDs) are stored in IDS. The IDS also contains the template workflows for buying and selling processes.

An adaptable workflow system architecture on the Internet for electronic commerce applications

An electronic commerce (EC) process is a business process and defining it as a workflow provides all the advantages that come with this technology. Yet electronic commerce processes place certain demands on the workflow technology like the distribution of the load of the workflow engine to multiple servers, dynamic modification of workflows for adaptability, openness and availability. We propose a workflow system architecture to address these issues. The componentwise architecture of the system makes it possible to incorporate the functionality and thus the complexity only when it is actually needed. The infrastructure of the system is based on CORBA 2.0 where methods are invoked through XML. The clients of the system are coded as network transportable applets written in Java so that the end user can activate workflow components through the workflow domain manager over the network. The system provides high availability by replicating the component server repository and the workflow domain manager. We also discuss how this architecture can be used in building an electronic marketplace.

Provision of market services for eCo compliant electronic marketplaces

The progress and wider dissemination of electronic commerce will be facilitated through interoperability infrastructures. Commerce Nets eCo framework is a promising effort in this direction. In the eCo framework, businesses participate in a marketplace through standard interfaces for their services and by exchanging standardized documents. This framework does not specify any further interfaces for the services a marketplace itself may offer.In this paper, we demonstrate that a rich set of marketplace-specific services such as automated discovery of the needed services, comparison shopping, and negotiation can be offered to market participants by introducing a marketplace as an eCo business. For this purpose, a previously developed marketplace, namely MOPPET, is made eCo-compliant. We demonstrate that introducing MOPPET as an eCo business increases the functionality of the eCo market in the sense that several market specific services become available to the market participants.

METU-Emar: An Agent-Based Electronic Marketplace on the Web

In this paper, we describe a scenario for a distributed marketplace on the Web where resource discovery agents find out about resources that may want to join the marketplace and electronic commerce is realized through buying agents representing the customers and the selling agents representing the resources like electronic catalogs. We propose a possible architecture which is based on the emerging technologies and standards. In this architecture, the resources expose their metadata using Resource Description Framework (RDF) to be accessed by the resource discovery agents and their content through Extensible Markup Language (XML) to be accessed by the selling agents by using Document Object Model (DOM). The marketplace contains Document Type Definitions (DTDs) and a dictionary of synonyms to be used by the buying agents to help the customer to specify the item s/he wishes to purchase. Distribution infrastructure is CORBA and Web on which the buying and selling agents find out about each other using Trading Object Services. The modifications necessary to the proposed architecture considering only the available technology are also discussed.