Autonomous Databases Research Articles

Query optimization via contention space partitioning and cost error controlling for dynamic multidatabase systems

A multidatabase system (MDBS) integrates information from multiple autonomous local databases. Performing global query optimization to achieve efficient query processing in such a system is challen...

Adaptive Index Utilization in Memory-Resident Structural Joins

We consider adaptive index utilization as a fine-grained problem in autonomic databases in which an existing index is dynamically determined to be used or not in query processing. As a special case, we study this problem for structural joins, the core operator in XML query processing, in the main memory. We find that index utilization is beneficial for structural joins only under certain join selectivity and distribution of matching elements. Therefore, we propose adaptive algorithms to decide whether to use an index probe or a data scan for each step of matching during the processing of a structural join operator. Our adaptive algorithms are based on the history, the look-ahead information, or both. We have developed a cost model to facilitate this adaptation and have conducted experiments with both synthetic and real-world data sets. Our results show that adaptively utilizing indexes in a structural join improves the performance by taking advantage of both sequential scans and index probes.

Execution of distributed queries in the web environment

Database query processing is one of the fundamental issues in data engineering, particularly when more and more databases become distributed over the Internet in the last decade. There have been several approaches to the problem of distributed query processing (DQP), some were successful in the client-server environment but not so in an environment with heterogeneous and autonomous databases. The challenge relies on the nature of the Internet and the Web that pose many difficulties to the problem in hand. In this paper, we propose a model that uses an XML standard and its equivalent in-memory data structure to achieve data sharing, and invokes XML Web services in asynchronous mode to allow local database management systems to efficiently process local data. This approach, like XJoin, allows progress to be made even when data sources experience delays. It builds a layer on top of existing database management systems to minimize the complexity and cost for processing distributed queries that is critical for making such a method practical.

A Scalable Middleware for Web Databases

The emergence of Web databases has introduced new challenges related to their organization, access, integration, and interoperability. New approaches and techniques are needed to provide across-the-board transparency for accessing and manipulating Web databases irrespective of their data models, platforms, locations, or systems. In meeting these needs, it is necessary to build a middleware infrastructure to support flexible tools for information space organization, communication facilities, information discovery, content description, and assembly of data from heterogeneous sources. In this paper, we describe a scalable middleware for efficient data and application access that we have built using the available technologies. The resulting system is called WebFINDIT. It is a scalable and uniform infrastructure for locating and accessing heterogeneous and autonomous databases and applications.

On mobile transaction processing in dynamically configurable mobile database communities

The topology of a mobile ad hoc network (MANET) may change randomly and rapidly at an unpredictable time, since nodes are free to move arbitrarily. In such an environment, we may have a collection of autonomous, distributed, heterogeneous and mobile databases (denoted mobile database community (MDBC)). This paper describes an approach for controlling concurrency of mobile transactions executed in MDBCs. The proposed approach is based on the use of semantic knowledge to relax the notion of absolute transaction atomicity. Supported by this new concept of atomicity, we propose a new correctness criterion, denoted mobile semantic serializability, for the execution of concurrent transactions in MDBCs. The proposed correctness criterion provides a high degree of inter-transaction parallelism and ensures consistency of the mobile database.

Query optimization in distributed networks of autonomous database systems

Large-scale distributed environments, where each node is completely autonomous and offers services to its peers through external communication, pose significant challenges to query processing and optimization. Autonomy is the main source of the problem, as it results in lack of knowledge about any particular node with respect to the information it can produce and its characteristics, for example, cost of production or quality of produced results. In this article, inspired by e-commerce technology, we recognize queries as commodities and model query optimization as a trading negotiation process. Subquery answers and subquery operator execution jobs are traded between nodes until deals are struck with some nodes for all of them. Such trading may also occur recursively, in the sense that some nodes may play the role of intermediaries between other nodes (subcontracting). We identify the key parameters of the overall framework and suggest several potential alternatives for each one. In comparison to trading negotiations for e-commerce, query optimization faces unique new challenges that stem primarily from the fact that queries have a complex structure and can be broken into smaller parts. We address these challenges through a particular instantiation of our framework focusing primarily on the optimization algorithms run on “buying” and “selling” nodes, the evaluation metrics of the queries, and the negotiation strategy. Finally, we present the results of several experiments that demonstrate the performance characteristics of our approach compared to those of traditional query optimization.

Networked database builder and data-mining engine for electronic journal papers

We have developed a data-warehouse system designed for research data centres, which is currently tested in the National Institute for Fusion Science (NIFS) in Japan. The data warehouse integrates an online builder of multi-dimensional numerical databases a crawler engine, which classifies the papers retrieved from various online databases of electronic journals for relevance. The present data warehouse functions as an autonomous intelligent database of scientific abstracts; it is also a precursor for an autonomous self-updating database of numerical data, our ultimate goal.

Implementing the European Transport Information System

The development of the Trans-European Networks and the formulation of a common transport policy are essential elements in the economic and social development of the European Union. Such activities require significant information about current status (passenger and freight transport volumes, congestion, environmental impacts, etc.) and reliable forecasts. The relevant information exists in dispersed, heterogeneous, and autonomous databases throughout Europe, as well as in pertinent transport studies. The European Transport Information System under development is intended to support decisions on transport policies and the Trans-European Transport Networks by accommodating policy-related information in a repository that will be kept up-to-date through well-defined procedures under the control of experts and will be accessible through an Internet-based software tool. A hierarchical structure of criteria, subcriteria, indicators, and variables is used to link policy questions to relevant data sets, which are populated by collected data and statistics or alternatively by data generated through the use of models. The scope of this current work is to give an overview of the structure, functionality, and current content (data sets, variables, indicators, etc.) of the information system above.

Implementing the European Transport Information System

The development of the Trans-European Networks and the formulation of a common transport policy are essential elements in the economic and social development of the European Union. Such activities require significant information about current status (passenger and freight transport volumes, congestion, environmental impacts, etc.) and reliable forecasts. The relevant information exists in dispersed, heterogeneous, and autonomous databases throughout Europe, as well as in pertinent transport studies. The European Transport Information System under development is intended to support decisions on transport policies and the Trans-European Transport Networks by accommodating policy-related information in a repository that will be kept up-to-date through well-defined procedures under the control of experts and will be accessible through an Internet-based software tool. A hierarchical structure of criteria, suberiteria, indicators, and variables is used to link policy questions to relevant data sets, which are p...

BACIIS

Life science Web databases are becoming increasingly essential in conducting everyday biological research. With more than 300 life science Web databases and the growing size of the life science data, searching and managing these complex data requires technology beyond that of traditional database systems. The open research issues include the interoperability of geographically distributed autonomous databases, which are generally only Web-accessible, and the seamless semantic-based integration of these databases with total transparency to the user. In this paper, the implementation of a Biological and Chemical Information Integration System (BACIIS) is presented. BACIIS supports the integration of multiple heterogeneous life science Web databases and allows the execution of global applications that extend beyond the boundaries of individual databases. This paper discusses the architecture of BACIIS. It also discusses the techniques used to extract and integrate data from the various life science Web databases.

Context Interchange Mediation for Semantic Interoperability and Dynamic Integration of Autonomous Information Sources in the Fixed Income Securities Industry

We examine semantic interoperability problems in the fixed income securities industry and propose a knowledge representation architecture for context interchange mediation to support dynamic integration of autonomous database, web, and procedural sources of information. For sources and receivers sharing a common subject domain, the mediator's reasoning engine can devise query plans integrating multiple sources and resolving semantic heterogeneity. Receiver applications can obtain the data they need in the form they need it without imposing changes on sources. The architecture includes: 1) data models for each source and receiver, 2) subject ontologies, containing abstract subject matter conceptualizations that would be known to experienced practitioners in the industry, and 3) context models for each source and receiver that explain how each data model implements the abstract concepts from a subject ontology.

Search engines in Internet and intellectual property

Those instruments lack any particular regulation for the time being in the spanish legal system. Although regarding the more generic question of the liability of the renderer of services, the Bill on e-commerce, pending its tramitation in the Parliament now (May 2002), deals with the topic of search engines (art. 17) 2 , contrasting with the absolute silence of the EU Directive 31/2000 on e-commerce. Going further of that prelegislative text, three main questions can be formulated about the intellectual property issues related to the search engines: 1) Can the results of the searches be protected as autonomous databases?; 2) Are the search engines databases on their own?; 3) Does their operation imply an unlawful extraction and/or reuse of the information they collect from other web sites or databases or, on the contrary, is this a lawful use (right to mention)?

Complex life science multidatabase queries

Recent advances in the development of new, high throughput screening technologies have resulted in a wealth of life science data. The complexity and volume of these data require technology beyond that of traditional database systems. Open research issues include the seamless, semantic-based integration of geographically distributed, autonomous web databases. Biological And Chemical Integration Information System (BACIIS) addresses these issues. This paper discusses the challenges associated with the integration of life science web databases and the techniques used in BACIIS to address these challenges. Particularly, the execution of life science, multidatabase queries is investigated, and an approach that can overcome the limitations of the query capabilities of each individual life science web database participating in the integration is presented. This approach hides the heterogeneity of the individual databases from the user while providing an efficient execution plan for complex, life science, multidatabase queries.

DATA CURRENCY QUALITY SATISFACTION IN THE DESIGN OF A DATA WAREHOUSE

A Data Warehouse (DW) is a large collection of data integrated from multiple distributed autonomous databases and other information sources. A DW can be seen as a set of materialized views defined over the remote source data. Until now research work on DW design is restricted to quantitatively selecting view sets for materialization. However, quality issues in the DW design are neglected. In this paper we suggest a novel statement of the DW design problem that takes into account quality factors. We design a DW system architecture that supports performance and data consistency quality goals. In this framework we present a high level approach that allows to check whether a view selection guaranteeing a data completeness quality goal also satisfies a data currency quality goal. This approach is based on an AND/OR dag representation for multiple queries and views. It also allows determining the minimal change propagation frequencies that satisfy the data currency quality goal along with the optimal query evaluation and change propagation plans. Our results can be directly used for a quality driven design of a DW.

Observations on recurrent syncope and presyncope in 641 patients

Syncope is a common disorder that is potentially disabling and affects both young and old. Once neurological, cardiological, and metabolic causes have been excluded, there remains a group in which diagnosis is unclear; some may have an autonomic basis. We therefore did a retrospective study on consecutive patients referred to our tertiary referral autonomic centres between 1992 and 1998 with recurrent syncope and presyncope, in whom non-autonomic causes, before referral, had been sought and excluded. The object was to find out whether autonomic investigation helped diagnosis. Data from case notes and from the autonomic database on 641 patients were analysed. Syncopal patients with a known or provisional diagnosis of autonomic failure were excluded from analysis. The role of screening tests in establishing or excluding an autonomic cause was assessed. Response to additional autonomic tests (such as head-up tilt with or without venepuncture, and food challenge and exercise) was documented. Some patients underwent further testing if non-autonomic neurological, psychiatric, and other disorders were considered. Screening autonomic function tests indicated orthostatic hypotension and confirmed chronic autonomic failure in 31 (4.8%) patients. Neurally mediated syncope was diagnosed in 279 (43.5%) on the basis of clinical features and autonomic testing. Most had vasovagal syncope (227 [35%]); other causes included carotid sinus hypersensitivity (37 [5.8%]), and a group of 15 (2.3%) were associated with rarer causes such as micturition and swallowing. Miscellaneous cardiovascular causes (systemic hypotension, arrhythmias), or drugs, contributed to syncope in 53 (8.3%). Non-autonomic neurological causes included vestibular dysfunction (32 [5%]) and epilepsy (11 [1.7%]). In 56 (8.7%) a psychiatric cause was thought to be contributory. In 179 (27.9%), syncope was of unknown cause. In recurrent syncope and presyncope, when cardiac, neurological, and metabolic causes have been excluded, autonomic investigation can aid management by making, confirming, or excluding various factors or diagnoses.

Design of an SHD-distributed database over IP to support telemedicine.

We have conducted tests utilizing superhigh-definition CRTs (hereafter, referred to as a "super high-definition image system," or "SHD ": 2,048 x 2,048 pixels, 24-bit RGB gradation, noninterlace system) for autonomous and distributed medical image database systems. The system is capable of providing six times the image definition of a hi-vision television (HDTV). The aim in designing and testing the system is to enable gigabit network connectivity while displaying images on a DOS- V machine. This paper discusses how we devised an integrated environment for managing and operating distributed an SHD image database to support Telemedicine linking with ATM, with INS-1500, and with dial-up IP connection.

Global scheduling for flexible transactions in heterogeneous distributed database systems

A heterogeneous distributed database environment integrates a set of autonomous database systems to provide global database functions. A flexible transaction approach has been proposed for the heterogeneous distributed database environments. In such an environment, flexible transactions can increase the failure resilience of global transactions by allowing alternate (but in some sense equivalent) executions to be attempted when a local database system fails or some subtransactions of the global transaction abort. We study the impact of compensation, retry, and switching to alternative executions on global concurrency control for the execution of flexible transactions. We propose a new concurrency control criterion for the execution of flexible and local transactions, termed F-serializability, in the error-prone heterogeneous distributed database environments. We then present a scheduling protocol that ensures F-serializability on global schedules. We also demonstrate that this scheduler avoids unnecessary aborts and compensation.

Controlling aggregation in distributed object systems: a graph-based approach

The Distributed Object Kernel is a federated database system providing a set of services which allow cooperative processing across different databases. The focus of this paper is the design of a DOK security service that provides for enforcing both local security policies, related to the security of local autonomous databases, and federated security policies, governing access to data aggregates composed of data from multiple distributed databases. We propose Global Access Control, an extended access control mechanism enabling a uniform expression of heterogeneous security information. Mappings from existing Mandatory and Discretionary Access Controls are described. To permit the control of data aggregation, the derivation of unauthorized information from authorized data, our security framework provides a logic-based language, the Federated Logic Language (FELL), which can describe constraints on both single and multiple states of the federation. To enforce constraints, FELL statements are mapped to state transition graphs which model the different subcomputations required to check the aggregation constraints. Graph aggregation operations are proposed for building compound state transition graphs for complex constraints. To monitor aggregation constraints, two marking techniques, called Linear Marking Technique and Zigzag Marking Technique, are proposed. Finally, we describe a three-layer DOK logical secure architecture enabling the implementation of the different security agents. This includes a Coordination layer, a Task layer, and a Database layer. Each contains specialized agents that enforce a different part of the federated security policy. Coordination is performed by the DOK Manager, enforcing security is performed by a specialized Constraint Manager agent, and the database functions are implemented by user and data agents.

Supporting dynamic interactions among Web-based information sources

The ubiquity of the World Wide Web offers an ideal opportunity for the deployment of highly distributed applications. Now that connectivity is no longer an issue, attention has turned to providing a middleware infrastructure that will sustain data sharing among Web-accessible databases. We present a dynamic architecture and system for describing, locating, and accessing data from Web-accessible databases. We propose the use of flexible organizational constructs service links and coalitions to facilitate data organization, discovery, and sharing among Internet-accessible databases. A language is also proposed to support the definition and manipulation of these constructs. The implementation combines Java, CORBA, database API (JDBC), agent, and database technologies to support a scalable and portable architecture interconnecting large networks of heterogeneous and autonomous databases. We report on an experiment to provide uniform access to a Web of healthcare-related databases.

An approach to interoperation between autonomous database systems

In this paper we present an approach to support interoperation between autonomous database systems. In particular, we concentrate on distributed information discovery and access for systems with a large number of databases. We avoid the need for integrated global schemas or centralized structures containing information on the available data and its location. We instead provide an architecture that supports data distribution, autonomy and heterogeneity. The architecture also supports system evolution by the addition and removal of databases. A distributed information discovery algorithm is provided to perform data requests, database location and data access. A feature of our approach is to distribute the information about database contents using simple hierarchical information structures composed of special terms. A prototype has been developed to demonstrate and evaluate the approach. A hospital case study is used to illustrate its feasibility and applicability.