Pinar Koksal

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.

METU interoperable database system

METU INteroperable Database System (MIND) is a multidatabase system that aims at achieving interoperability among heterogeneous, federated DBMSs. MIND architecture if based on OMG distributed object management model. It is implemented on top of a CORBA compliant ORB, namely, ObjectBroker. MIND provides users a single ODMG-93 compliant common data model, and a single global query language based on SQL. This makes it possible to incorporate both relational and object oriented databases into the system. Currently Oracle 7, Sybase and METU OODBMS (MOOD) have been incorporated into MIND. The main components of MIND are a global query processor, a global transaction manager, a schema integrator, interfaces to supported database systems and a user graphical interface.In MIND all local databases are encapsulated in a generic database object with a well defined single interface. This approach hides the differences between local databases from the rest of the system. The integration of export schemas is currently performed manually by using an object definition language (ODL) which is based on OMGs interface definition language. The DBA builds the integrated schema as a view over export schemas. the functionalities of ODL allow selection and restructuring of schema elements from existing local schemas.MIND global query optimizer aims at maximizing the parallel execution of the intersite joins of the global subqueries. Through MIND global transaction manager, the serializable execution of the global transactions are provided.

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.

A multidatabase system implementation on CORBA

METU Interoperable DBMS (MIND) is a multidatabase system based on OMGs distributed object management architecture. It is implemented on top of a CORBA compliant ORB, namely, DECs ObjectBroker. In MIND, all local databases are encapsulated in a generic database object. The interface of the generic database object is defined in CORBA IDL and multiple implementations of this interface, one for each component DBMS, namely Sybase, Adabas D and MOOD are provided. MIND provides its users with a common data model and a single global query language based on SQL. The main components of MIND are a global query manager, a global transaction manager, a schema integrator, interfaces to supported database systems and a graphical user interface. The integration of export schemas is currently performed by using an object definition language (ODL) which is based on OMGs interface definition language. MIND global query optimizer aims at maximizing the parallel execution of the intersite operations of the global subqueries. Through the MIND global transaction manager, the serializable execution of the global transactions (both nested and flat) is provided.

Dynamic query optimization on a distributed object management platform

A Distributed Object Management (DOM) architecture, when used as the infrastructure of a multidatabase system, not only enables easy and flexible interoperation of D13MSS, but also facilitates interoperation of the multidatabase system with other repositories that do not have DIBMS capabilities. Thk is an important advantage, since most of data still resides on repositories that do not have DIBMS capabilities. In thk paper, we describe a dynamic query optimization technique for a multidatabaae system, namely MIND, implement ed on a DOM environment. Dynamic query optimization, which schedules intersite operations at runtime, fits better to such an environment since it benefits from location transparency provided by the DOM framework. In thk way, the dynamic changes in the configuration of system resources such as a relocated DBMS or a new mirror to an existing DBMS, do not affect the optimized query execution in the system. Furthermore, the uncertainty in estimating the appearance times (i.e., the execution time of the global subquery at a local DBMS) of partial results are avoided because there is no need for the dynamic optimizer to ‘know the logical cost parameters of the underlying local DBMS. In scheduling the intersite operations a statistical decision mechanism is used. We also consider the schema inte~ation information to make room for further query optimizak ion. For this purpose, a method is presented that forms global query graphs by taking the schema integration information into account which is then used by the dynamic query optimizer. The proposed scheme tries to exploit the inherent parallelism in the system as much as possible. The performance of the developed method is compared with two other most related techniques and the results clf the * This work is partially being supported by the Turkish State PIanning Organization, Project Number: AF P-0312 DPT.95K120500, by the Scientific and Technical Research Council of Turkey, Project Number: EEEAG-Yazilim5, by Motorola (USA) and by Sevgi Holding (’Ihrkey) Permission to make digitsVbard copies of nli or part of thk material for personal or class~m use is granted without fee provided that the copies are not made or dwtributed for profit or commercial advantage, the copyright notice, the title of the publication and its date appear, and notice is given that copyright is by permission of rbe ACM, Inc. To copy otherwise, to republish, to poston serversor to redistributeto lists, requireaspecific permissionand/or fee. CIKM 96, Rockville MD USA @ 199(j ACM @89791 +73+/9fj/l 1 ..

A workflow-based electronic marketplace on the Web

3 .5~ 117 experiments indicate that the dynamic query optimization technique presented in thk paper has a better performance.

A Component-Based Workflow System with Dynamic Modifications

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.

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

Adapting to changes in its environment dynamically is a very important aspect of workflow systems. In this paper, we propose a component-based workflow system architecture specifically designed for this purpose. To allow for easy modification of workflow instances, an instance is designed as an object that contains all the necessary data and control information as well as its execution history. This feature facilitates to dynamically modify the process definition on instance basis at run time. The system is designed to consist of functional components like, Basic Enactment Service, History Manager, Workflow Monitoring Tool, Dynamic Modification Tool, etc. The clients of the system are coded as network-transportable applets written in Java so that the end user can activate workflow system components by connecting to the Workflow Domain Manager over the Internet. In this paper we also present a workflow process definition language FLOWDL, its graphical representation FLOWGRAPH and a workflow process modification language FLOWML and illustrate how the modification process is handled.

Dynamic Query Optimization in Multidatabases.

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.