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Full-Text Articles in Physical Sciences and Mathematics

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 …


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 …


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 …


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.


Supporting Search For Reusable Software Objects, T. Isakowitz, Robert J. Kauffman Jun 1996

Supporting Search For Reusable Software Objects, T. Isakowitz, Robert J. Kauffman

Research Collection School Of Computing and Information Systems

Prior research has shown that achieving high levels of software reuse in the presence of repository and object-based computer-aided software engineering (CASE) development methods presents interesting human, managerial and technical challenges. This article presents research that seeks to enhanced software development performance through reuse. We propose automated support for developers who search large repositories for the appropriate reusable software objects. We characterize search for repository objects in terms of a multistage model involving screening, identification, and the subsequent choice between new object construction or reusable object implementation. We propose automated support tools, including ORCA, a software Object Reuse Classification Analyzer, …


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 …


On The Complexity Of Manpower Shift Scheduling, Hoong Chuin Lau Jan 1996

On The Complexity Of Manpower Shift Scheduling, Hoong Chuin Lau

Research Collection School Of Computing and Information Systems

We consider the shift assignment problem in manpower scheduling, and show that a restricted version of it is NP-hard by a reduction from 3SAT. We then present polynomial algorithms to solve special cases of the problem and show how they can be deployed to solve more complex versions of the shift assignment problem. Our work formally defines the computational intractibility of manpower shift scheduling and thus justifies existing works in developing manpower scheduling systems using combinatorial and heuristic techniques.