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Databases and Information Systems

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Articles 781 - 808 of 808

Full-Text Articles in Numerical Analysis and Scientific Computing

Web Warehousing System: Design And Issues, Wee-Keong Ng, Ee Peng Lim, Sourav S. Bhowmick, Sanjay Kumar Madria Nov 1998

Web Warehousing System: Design And Issues, Wee-Keong Ng, Ee Peng Lim, Sourav S. Bhowmick, Sanjay Kumar Madria

Research Collection School Of Computing and Information Systems

The World Wide Web is a distributed global information resource. It contains a large amount of information that have been placed on the web independently by different organizations and thus, related information may appear across different web sites. To manage and access heterogeneous information on WWW, we have started a project of building a web warehouse, called Whoweda (Warehouse of Web Data). Currently, our work on building a web warehousing system has focused on building a data model and designing a web algebra. In this paper, we discuss design and research issues in a web warehousing system. The issues include …

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Information Coupling In Web Databases, Sourav S. Bhowmick, Wee-Keong Ng, Ee Peng Lim Nov 1998

Information Coupling In Web Databases, Sourav S. Bhowmick, Wee-Keong Ng, Ee Peng Lim

Research Collection School Of Computing and Information Systems

Web information coupling refers to an association of topically related web documents. This coupling is initiated explicitly by a user in a web warehouse specially designed for web information. Web information coupling provides the means to derive additional, useful information from the WWW. In this paper, we discuss and show how two web operators, i.e., global web coupling and local web coupling, are used to associate related web information from the WWW and also from multiple web tables in a web warehouse. This paper discusses various issues in web coupling such as coupling semantics, coupling-compability, and coupling evaluation.

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A Global Object Model For Accommodating Instance Heterogeneities, Ee Peng Lim, Roger Hsiang-Li Chiang Nov 1998

A Global Object Model For Accommodating Instance Heterogeneities, Ee Peng Lim, Roger Hsiang-Li Chiang

Research Collection School Of Computing and Information Systems

To completely address database integration problems in the context of multidatabase [10] and data warehousing systems, one has to examine various integration and query requirements. Due to various reasons such as poor data quality in local databases, ongoing local database updates, and instance heterogeneities, some instance differences have to be accommodated by the integrated databases. We have therefore proposed a new object-oriented global data model, called OORA, that can accommodate attribute and relationship instance heterogeneities in the integrated database. In addition, the OORA model has been designed to allow database integrators and end users to query both the local and …

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Design And Implementation Of A Maritime Conflict Prediction System, Wee-Keong Ng, Ee Peng Lim, Wen Jing Hsu, Yy Cao Oct 1998

Design And Implementation Of A Maritime Conflict Prediction System, Wee-Keong Ng, Ee Peng Lim, Wen Jing Hsu, Yy Cao

Research Collection School Of Computing and Information Systems

Maritime conflicts have serious impacts on Singapore and the surrounding region both economically and environmentally. This is particularly severe for conflicts such as collisions between large vessels or tankers carrying oil and chemicals. Thus, it is in the interests of the Maritime and Port Authority of Singapore (MPA) to avoid collisions or near-collisions among such vessels navigating through Singapore waters. Existing systems used by MPA predict potential maritime conflicts arising within a short and fixed time horizon. The system produces inconsequential warnings that are often ignored. In this paper, we describe an advanced computerbased system designed to assist in the …

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Join Processing In Web Databases, Sourav S. Bhowmick, Wee-Keong Ng, Ee Peng Lim Aug 1998

Join Processing In Web Databases, Sourav S. Bhowmick, Wee-Keong Ng, Ee Peng Lim

Research Collection School Of Computing and Information Systems

Recently, there has been increasing interests in data models and query languages for unstructured data in the World Wide Web. When web data is harnessed in a web warehouse, new and useful information can be derived through appropriate information manipulation. In our web warehousing project, we introduce a new operator called the web join. Like its relational counterpart, web join combines information from two web tables to yield a new web table. This paper discusses various issues in web join such as join semantics, joinability, and join evaluation.

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Querying Structured Web Resources, Ee Peng Lim, Cheng Hai Tan, Boon Wan Lim, Wee-Keong Ng Jun 1998

Querying Structured Web Resources, Ee Peng Lim, Cheng Hai Tan, Boon Wan Lim, Wee-Keong Ng

Research Collection School Of Computing and Information Systems

To provide query facilities over Web resources, several web search engines such as Yahoo, Altavista, Infoseek, etc. have been developed. Most prominently, web search engines have been used to index all web pages on the Internet. The queries supported by these search engines are mainly designed to reveal web pages that meet the search criteria specified by the users. In this way, the search engines have been used as some kind of discovery tools. The queries supported are known as discovery queries. On the other hand, a web search engine can also be used to index and support queries over …

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Database Selection Techniques For Routing Bibliographic Queries, Ee Peng Lim, Wee-Keong Ng, Jian Xu, Yinyan Cao Jun 1998

Database Selection Techniques For Routing Bibliographic Queries, Ee Peng Lim, Wee-Keong Ng, Jian Xu, Yinyan Cao

Research Collection School Of Computing and Information Systems

No abstract provided.

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An Interlibrary Loan System On The World Wide Web, Schubert Shou Boon Foo, Ee Peng Lim Jan 1998

An Interlibrary Loan System On The World Wide Web, Schubert Shou Boon Foo, Ee Peng Lim

Research Collection School Of Computing and Information Systems

Inter-Library Loan (ILL) service is one of the services provided by libraries that offers users a way to access library resources beyond their affiliated libraries. Additionally, it allows participating libraries to share and maximize their resources. This work examines the ILL process used by libraries in Singapore and proposes that the existing paper-based manual system be replaced by a Web-based ILL system. Such a Web-based system has been successfully designed and implemented at the Nanyang Technological University. The paper presents an overview of the system requirements and architecture, implementation details and demonstrates the feasibility and advantages of the new system.

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Evaluation Of Information Modeling Methods: A Review, Keng Siau, Matti Rossi Jan 1998

Evaluation Of Information Modeling Methods: A Review, Keng Siau, Matti Rossi

Research Collection School Of Computing and Information Systems

Hundreds of modeling methods are in existence today. Yet practitioners and researchers are zealously "producing" new modeling methods. The "blooming" of modeling methods is not the problem; the lack of standardize techniques for evaluating them is. To further complicate the matter, most of the modeling methods are introduced based on common sense and intuition. Theoretical foundations and empirical evidence are severely lacking. With the current state of affairs, evaluation of modeling methods has become necessary. Comparing modeling methods provides us with the necessary knowledge and understanding on the strengths and weaknesses of each method. This knowledge can also guide us …

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Source-Aware Multidatabase Query Processing, Ee Peng Lim, Yinyan Cao, Roger Hsiang-Li Chiang May 1997

Source-Aware Multidatabase Query Processing, Ee Peng Lim, Yinyan Cao, Roger Hsiang-Li Chiang

Research Collection School Of Computing and Information Systems

We introduce a multidatabase model to represent the information that derives from different local databases. This model, known as Tuple-Source (TS) relational model, accommodates tuples from different local databases by attaching them with their source information in the global relations which are also known as TS-relations. In other words, a source attribute is implicit in every TS-relation. To manipulate the global relations, we have developed the TSSQL query language and implemented a distributed query processor to process such queries. In this paper, we report our distributed query processing architecture and algorithms. Our architecture consists of a query mediator and a …

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Distributed Query Processing For Structured And Bibliographic Databases, Ee Peng Lim, Ying Lu Apr 1997

Distributed Query Processing For Structured And Bibliographic Databases, Ee Peng Lim, Ying Lu

Research Collection School Of Computing and Information Systems

To support future digital library systems which draw information from different sources on the internet, we have to provide integrated queries to pre-existing database servers which contain structured, semi-structured and unstructured data. In this paper, we specifically examine the problem of querying both existing structured relational databases and bibliographic databases. By adopting the well-accepted Z39.50 standard protocol to access bibliographic databases in different legacy library systems, we have developed an extended SQL model, known as HarpSQL, to support integrated queries to both SQL databases and bibliographic databases. Using HarpSQL, one can not only query bibliographic databases in an SQL manner, …

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Integrated Queries To Existing Bibliographic And Structured Databases, Ee Peng Lim, Ying Lu Jan 1997

Integrated Queries To Existing Bibliographic And Structured Databases, Ee Peng Lim, Ying Lu

Research Collection School Of Computing and Information Systems

It is widely accepted that future digital library applications have to be built upon different kinds of database servers to draw upon different forms of data, including bibliographic, text, multimedia, and structured data. In this paper, the problem of integrating existing public bibliographic databases and structured databases which reside at different locations in the network is addressed. Although bibliographic data is semistructured, its attribute set is often determined by an international standard known as MARC. To unify bibliographic and structured data, the well-known SQL was extended to model bibliographic related attributes and queries. In particular, a new data type was …

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A Hypermedia Database To Manage World-Wide-Web Documents, Schubert Shou Boon Foo, Ee Peng Lim Jan 1997

A Hypermedia Database To Manage World-Wide-Web Documents, Schubert Shou Boon Foo, Ee Peng Lim

Research Collection School Of Computing and Information Systems

The surge of interest in the World-Wide-Web (WWW) with its potential commercial payoff has resulted in an explosion of information as organisations join in to publish and do business on the Internet. A related development, Intranet, which basically uses the same technology to build private corporate WWW-based networks, has emerged to provide cost-effective and efficient groupware and information management solutions for organisations. As a result, the Hyper Text Markup Language (HTML), used for constructing WWW documents, has become a contender for authoring future office documents. With this scenario, this study examines WWW practices and highlights the inadequacy and drawbacks of …

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Managing World Wide Web Publications, Schubert Foo, Ee Peng Lim Jan 1997

Managing World Wide Web Publications, Schubert Foo, Ee Peng Lim

Research Collection School Of Computing and Information Systems

The surge of interest in the World Wide Web (WWW), with its potential commercial payoff, has resulted in an explosion of information as organizations join in the fray to publish and do business on the Internet. In addition, Intranet, the private corporate WWW‐based network, has also emerged to provide cost‐effective and efficient groupware and information management solutions for organizations. As a result, the HyperText Markup Language used for constructing WWW documents has become a contender for authoring future office documents. Examines the current practices of WWW publishing and highlights its inadequacies and drawbacks. Demonstrates the need and advantages of using …

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Export Database Derivation Approach For Supporting Object-Oriented Wrapper Queries, Ee Peng Lim, Hon-Kuan Lee Dec 1996

Export Database Derivation Approach For Supporting Object-Oriented Wrapper Queries, Ee Peng Lim, Hon-Kuan Lee

Research Collection School Of Computing and Information Systems

Wrappers export the schema and data of existing heterogeneous databases and support queries on them. In the context of cooperative information systems, we present a flexible approach to specify the derivation of object-oriented (OO) export databases from local relational databases. Our export database derivation consists of a set of extent derivation structures (EDS) which defines the extent and deep extent of export classes. Having well-defined semantics, the EDS can be readily used in transforming wrapper queries to local queries. Based on the EDS, we developed a wrapper query evaluation strategy which handles OO queries on the export databases. The strategy …

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An Evidential Reasoning Approach To Attribute Value Conflict Resolution In Database Integration, Ee Peng Lim, Jaideep Srivastava, Shashi Shekhar Oct 1996

An Evidential Reasoning Approach To Attribute Value Conflict Resolution In Database Integration, Ee Peng Lim, Jaideep Srivastava, Shashi Shekhar

Research Collection School Of Computing and Information Systems

Resolving domain incompatibility among independently developed databases often involves uncertain information. DeMichiel [1] showed that uncertain information can be generated by the mapping of conflicting attributes to a common domain, based on some domain knowledge. In this paper, we show that uncertain information can also arise when the database integration process requires information not directly represented in the component databases, but can be obtained through some summary of data. We therefore propose an extended relational model based on Dempster-Shafer theory of evidence [2] to incorporate such uncertain knowledge about the source databases. The extended relation uses evidence sets to represent …

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On Integrating Existing Bibliographic Databases And Structured Databases, Ying Lu, Ee Peng Lim Aug 1996

On Integrating Existing Bibliographic Databases And Structured Databases, Ying Lu, Ee Peng Lim

Research Collection School Of Computing and Information Systems

It is widely accepted that future digital library applications have to be built upon different kinds of database servers to draw different forms of data from them. These data include bibliographic data, text data, multimedia data, and structured data. We address the problem of integrating existing bibliographic and structured databases which reside at different locations in the network. To integrate bibliographic data and structured data, we extended the well-known SQL model to represent bibliographic related attributes and queries. In particular, we have added a new data type to model attributes in the bibliographic database. We have also designed specialized predicates …

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Specifying Object-Oriented Federated Database From Existing Databases, Ee Peng Lim, M. L. Lim, J. Srivastava Jun 1996

Specifying Object-Oriented Federated Database From Existing Databases, Ee Peng Lim, M. L. Lim, J. Srivastava

Research Collection School Of Computing and Information Systems

In this paper, we present a mapping strategy that is based on a proposed set of DB integration operations. We first define an OO federated DB as a virtual view on multiple OO export DBs. Our DB mapping strategy systematically derives each of the class extents, deep class extents and relationships of the federated DB using an operator tree consisting of the integration operations. This mapping approach differs from the other existing approaches in that it is algebraic based, and is therefore very suitable for implementing federated query processing.

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Gnarly Rantings About The Hacker And The Ants, Rudy Rucker May 1996

Gnarly Rantings About The Hacker And The Ants, Rudy Rucker

SWITCH

The article is an excerpt from Rucker’s book “The Happy Mutant”. It begins with his reflection of his career with GoMotion. He discusses the relation that he saw between design and cyberspace. Later he discusses his experience with a game a colleague found on the net: a virtual world where player is an ant. He talks about the struggles he goes through in this virtual world because of game difficulty and poor visuals. He ties it all in with how the Silicon Valley works in a similar way, and is filled with hackers and programers all needing each other to …

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How I Got Gnarly, Rudy Rucker May 1996

How I Got Gnarly, Rudy Rucker

SWITCH

The article describes how Rudy Rucker’s curious interest in celluar automata led to his career in mathematical computer science at San José State University. After conducting interviews on the theory of cellular automata as a freelance writer, he felt compelled to be involved in this great intellectual revolution in computer-aided experimental mathematics. Committed to reinventing himself, Rucker's interactions with mathematicians inspired him to write “Mind Tools”, a book that surveys mathematics from the standpoint that is information. After publishing his book, in 1987, he was eventually offered a position at SJSU in the Mathematics and Computer Science department. With assistance …

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Entity Identification In Database Integration, Ee Peng Lim, Jaideep Srivastava, Satya Prabhakar, James Richardson Feb 1996

Entity Identification In Database Integration, Ee Peng Lim, Jaideep Srivastava, Satya Prabhakar, James Richardson

Research Collection School Of Computing and Information Systems

The objective of entity identification is to determine the correspondence between objective instances from more than one database. This paper examines the problem at the instance level assuming that schema level heterogeneity has been resolved a priori. Soundness and completeness are defined as the desired properties of any entity-identification technique. To achieve soundness, a set of identity and distinctness rules have to be established for the entities in the integrated world. We then propose the use of extended key, which is the union of keys (and possibly other attributes) from the relations to be matched, and its corresponding identity rule …

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Multiclass Query Scheduling In Real-Time Database Systems, Hwee Hwa Pang, Michael J. Carey, Miron Livny Aug 1995

Multiclass Query Scheduling In Real-Time Database Systems, Hwee Hwa Pang, Michael J. Carey, Miron Livny

Research Collection School Of Computing and Information Systems

In recent years, a demand for real-time systems that can manipulate large amounts of shared data has led to the emergence of real-time database systems (RTDBS) as a research area. This paper focuses on the problem of scheduling queries in RTDBSs. We introduce and evaluate a new algorithm called Priority Adaptation Query Resource Scheduling (PAQRS) for handling both single class and multiclass query workloads. The performance objective of the algorithm is to minimize the number of missed deadlines, while at the same time ensuring that any deadline misses are scattered across the different classes according to an administratively-defined miss distribution. …

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Multiple Query Optimization With Depth-First Branch-And-Bound And Dynamic Query Ordering, Ee Peng Lim, Ahmet Cosar, Jaideep Srivastava Jan 1995

Multiple Query Optimization With Depth-First Branch-And-Bound And Dynamic Query Ordering, Ee Peng Lim, Ahmet Cosar, Jaideep Srivastava

Research Collection School Of Computing and Information Systems

In certain database applications such as deductive databases, batch query processing, and recursive query processing etc., usually a single query gets transformed into a set of closely related database queries. Also, great benefits can be obtained by executing a group of related queries all together in a single unified multi-plan instead of executing each query separately. In order to achieve this Multiple Query Optimization (MQO) identifies common task(s) (e.g. common subexpressions, joins, etc.) among a set of query plans and creates a single unified plan (multi-plan) which can be executed to obtain the required outputs for all queries at once. …

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Asynchronous Transaction Commitment In Federated Database Systems, San-Yih Hwang, Ee Peng Lim, Jaideep Srivastava Dec 1993

Asynchronous Transaction Commitment In Federated Database Systems, San-Yih Hwang, Ee Peng Lim, Jaideep Srivastava

Research Collection School Of Computing and Information Systems

We propose a new (and restricted) model for global transactions which allows asynchronous commitment of subtransactions. Our model requires each global transaction to have a fixed structure with update to the data in at most one database. Based on this transaction model, we present two concurrency control algorithms, namely Asynchronous Site Graph and Asynchronous VirtGlobalSG, which employ asynchronous commitment and achieve global serializability. Compared to other proposed algorithms, our algorithms employ asynchronous commitment so as to increase transaction performance. Furthermore, our algorithms do not put restrictions on transaction data access or local histories.

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Query Optimization And Processing In Federated Database Systems, Ee Peng Lim, Jaideep Srivastava Nov 1993

Query Optimization And Processing In Federated Database Systems, Ee Peng Lim, Jaideep Srivastava

Research Collection School Of Computing and Information Systems

No abstract provided.

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Multiple Query Optimization With Depth-First Branch-And-Bound, Ahmet Cosar, Ee Peng Lim, Jaideep Srivastava Nov 1993

Multiple Query Optimization With Depth-First Branch-And-Bound, Ahmet Cosar, Ee Peng Lim, Jaideep Srivastava

Research Collection School Of Computing and Information Systems

In certain database applications such as deductive databases, batch query processing, and recursive query processing etc., a single query can be transformed into a set ofclosely related database queries. Great benefits can be obtained by executing a group of related queries all together in a single unijied multi-plan instead of executing each query separately. In order to achieve this, Multiple Query Optimization (MQO) identifies common task(s) (e.g. common subezpressions, joins, etc.) among a set of query plans and creates a single unified plan (multiplan) which can be executed to obtain the required outputs forall queries at once. In this paper, …

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Entity Identification In Database Integration: An Evidential Reasoning Approach, Ee Peng Lim, Jaideep Srivastava Sep 1993

Entity Identification In Database Integration: An Evidential Reasoning Approach, Ee Peng Lim, Jaideep Srivastava

Research Collection School Of Computing and Information Systems

Entity identification is the problem of matching object instances from different databases which correspond to the same real-world entity. In this paper, we present a 2-step entity identification process in which attributes for matching tuples may be missing in certain tuples, and thus need to be derived prior to the matching. To match tuples, we require identity rules which specify the conditions to be satisfied by a pair of tuples, from different databases, before they can be considered as modeling the same real-world entity. We also introduce ILFD's (instance-level functional dependencies) as a form of inference rules which derive the …

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Entity Identification In Database Integration, Ee Peng Lim, Jaideep Srivastava, Satya Prabhakar, James Richardson Apr 1993

Entity Identification In Database Integration, Ee Peng Lim, Jaideep Srivastava, Satya Prabhakar, James Richardson

Research Collection School Of Computing and Information Systems

The objective of entity identification is to determine the correspondence between object instances from more than one database. Entity identification at the instance level, assuming that schema level heterogeneity has been resolved a priori, is examined. Soundness and completeness are defined as the desired properties of any entity identification technique. To achieve soundness, a set of identity and distinctness rules are established for entities in the integrated world. The use of extended key, which is the union of keys, and possibly other attributes, from the relations to be matched, and its corresponding identify rule are proposed to determine the equivalence …

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