this paper, we present the Pre-Serialization (PS) transaction management technique for the mobile multidatabase environment. This technique addresses disconnection and migration and enforces a range of atomicity and isolation criteria. We also develop an analytical model to compare the performance of the PS technique to that of the Kangaroo model. 1. Introduction A Multidatabase System (MDBS) is a federation of preexisting database systems, and is the natural result of shifting priorities and the need of an organization to be part of a greater information system [7]. In the Asilomar report [1], the authors state that "in the future, billions of web clients will be accessing millions of databases, and that the world wide web will be one large federated system". The rapid advances in wireless communication technology dictates that these static database systems extend their services to the mobile user. Transaction management in the Mobile Multidatabase (MMDB) environm

. A warehouse is a data repository containing integrated information for efficient querying and analysis. Maintaining the consistency of warehouse data is challenging, especially if the data sources are autonomous and views of the data at the warehouse span multiple sources. Transactions containing multiple updates at one or more sources, e.g., batch updates, complicate the consistency problem. In this paper we identify and discuss three fundamental transaction processing scenarios for data warehousing. We define four levels of consistency for warehouse data and present a new family of algorithms, the Strobe family, that maintain consistency as the warehouse is updated, under the various warehousing scenarios. All of the algorithms are incremental and can handle a continuous and overlapping stream of updates from the sources. Our implementation shows that the algorithms are practical and realistic choices for a wide variety of update scenarios. Keywords: data warehouse, data consistenc...

Cooperative information systems consist of existing legacy systems integrated in terms of a generic architecture which supports data integration and coordination among the integrated components. This paper presents a proposal for a generic integration architecture named CoopWARE. The architecture is presented in terms of the mechanisms it provides for data integration, and coordination. Data integration is supported by an information repository with an extensible schema, while coordination is facilitated by a rule set and an eventdriven rule execution mechanism. In addition, the paper describes implementation and application experiences for the architecture in the context of a 3-year software engineering project. keywords: cooperative information systems 1 Introduction Traditionally, information systems have been defined as software systems consisting of databases, application programs and user interfaces. However, current trends in business organizations point to a paradigm shift in...

. Workflow Management is a technique to integrate and automate the execution of steps that comprise a complex process, e:g:; a business process. Workflow Management Systems (WFMSs) primarily evolved from industry to cater to the growing demand for office automation tools among businesses. Coincidentally, database researchers developed several extended transaction models to handle similar applications. Although the goals of both the communities were the same, the issues they focused on were different. The workflow community primarily focused on modeling aspects to accurately capture the data and control flow requirements between the steps that comprise a workflow, while the database community focused on correctness aspects to ensure data consistency of sub-transactions that comprise a transaction. However, we now see a confluence of some of the ideas, with additional features being gradually offered by WFMSs. This paper provides an overview of correctness in workflow management. Correct...

A workflow is a long-duration multi-step activity. The task of the workflow manager is to automate the execution and the control of the workflow activities. In this paper we are interested in workflows that execute under the control of various processing stations that may be located at different nodes of a distributed system. The stations may be autonomous and only partially automated. We present the design and a proposed implementation of a new model for workflow management. The model presented is modular in the sense that modification of a subactivities of the workflow does not necessarily require changes to the workflow specification. Furthermore, the model preserves the autonomy of the individual office environments and does not require them to modify the means they use to process the individual steps of the activity.

Abstract. This article presents a theoretical basis for global concurrency control to maintain global serializability in multidatabase systems. Three correctness criteria are formulated that utilize the intrinsic characteristics of global transactions to determine the serialization order of global subtransactions at each local site. In particular, two new types of serializability, chain-conflicting serializability and sharing serializability, are proposed and hybrid serializability, which combines these two basic criteria, is discussed. These criteria offer the advantage of imposing no restrictions on local sites other than local serializability while retaining global serializability. The graph testing techniques of the three criteria are provided as guidance for global transaction scheduling. In addition, an optimal property of global transactions for determinating the serialization order of global subtransactions at local sites is formulated. This property defines the upper limit on global serializability in multidatabase systems. Key Words. Chain-conflicting serializability, sharing serializability, hybrid serializability, optimality.

In a number of application environments (e.g., computer aided design), serializability, the traditionally accepted notion of correctness has been found to be too restrictive, and a number of alternate criteria have been proposed in the literature. One such criterion is predicate-wise serializability (PWSR), which requires only restrictions of schedules that access subsets of the database over which integrity constraints are defined, to be serializable. In this paper, we identify restrictions on the structure of transaction programs, their concurrent execution and their access characteristics under which PWSR schedules preserve database consistency.

During the last years our research efforts were inspired by two different needs. On one side the number of non-expert users accessing databases is largely growing. On the other side, information systems will be no longer composed by a single centralised architecture, but rather by several heterogeneous component systems. In order to address such needs we have designed a new query system, having both user-oriented and multidatabase features. The system main components are an adaptive visual interface, providing the user with different and interchangeable interaction modalities, and a "translation layer", which creates and offers to the user the illusion of a single homogeneous schema out of several heterogeneous components. Both components are founded on a common ground, i.e. a formally defined and semantically rich data model, the Graph Model, and a minimal set of Graphical Primitives, in terms of which general query operations may be visually expressed. The Graph Model has...

As the demand for ever-larger knowledge bases grows, knowledge base management techniques assume paramount importance. In this paper we show that large, multi-user knowledge bases need concurrency control. We discuss known techniques from database concurrency control and explain their inadequacies in the context of knowledge bases. We offer a concurrency control algorithm, called the Dynamic Directed Graph (DDG) policy that addresses the specific needs of knowledge bases. The DDG policy exploits the rich structure of a knowledge base to support the interleaved, concurrent execution of several user requests, thereby improving overall system performance. We give a proof of correctness of the proposed concurrency control algorithm and an analysis of its properties. We demonstrate that these results from concurrency control interact in interesting ways with knowledge base features and highlight the importance of performanceoriented tradeoffs in the design of knowledge...

We describe an approach to the realisation of CIM systems through the coordination of autonomous component systems based on the exploitation of multi-database technologies. Each component system is augmented by a CIM Agent which provides a coordination interface; the interface specifies globally important local objects in terms of a global semantic model. System-wide consistency is ensured through the management of global constraints by a central coordinator along with cooperative multi-level transaction schemes. The CIM Agents are responsible for monitoring local activities and notifying the central coordinator of updates relevant to global consistency; they are also responsible for initiating local actions necessary for the maintenance of systemwide consistency as delegated by the coordinator. In particular, we describe the CIM/Z system which is being developed as part of a Swiss collaborative project on the use of database technologies for CIM. 1 Introduction A CIM system supports t...