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APPLIED INTELLIGENCE 1994年第2期4卷 133-156页

作者： STAUDT, M NISSEN, HW JEUSFELD, MA 1. Informatik V RWTH Aachen Ahornstr. 55 52056 Aachen Germany

The ideal query language for a knowledge base will probably never be found: easy formulation and easy evaluation of queries are two conflicting goals. Easy formulation asks for a flexible, expressive language near to human language or gestures. Easy evaluation of queries requires an effective mapping to machine code, which computes the correct answer in a finite number of steps. This article approaches the problem by a query language with three faces. The first projects queries to concepts of the knowledge representation language KL-One for easy formulation and readability. The second presents queries as rules of a deductive database with fixpoint semantics. The third presents queries as classes whose instances are the materialized answer (view) to the query. The methods for maintaining and updating the views are compiled from their deductive interpretation.

关键词： QUERY LANGUAGES object-oriented databases DEDUCTIVE databases VIEW MAINTENANCE INTENTIONAL UPDATES SUBSUMPTION

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TEMPORAL AND REAL-TIME databases - A SURVEY

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IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING 1995年第4期7卷 513-532页

作者： OZSOYOGLU, G SNODGRASS, RT UNIV ARIZONA DEPT COMP SCI TUCSON AZ 85721 USA

A temporal database contains time-varying data. In a real-time database transactions have deadlines or timing constraints. In this paper we review the substantial research in these two previously separate areas. First we characterize the time domain;then we investigate temporal and real-time data models. We evaluate temporal and real-time query languages along several dimensions. We examine temporal and real-time DBMS implementation. Finally, we summarize major research accomplishments to date and list several unanswered research questions.

关键词： object-oriented databases RELATIONAL databases QUERY LANGUAGES TEMPORAL DATA MODELS TIME-CONSTRAINED databases TRANSACTION TIME USER-DEFINED TIME VALID TIME

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Polymorphism and type inference in database programming

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ACM TRANSACTIONS ON DATABASE SYSTEMS 1996年第1期21卷 30-76页

作者： Buneman, P Ohori, A KYOTO UNIV MATH SCI RES INST SAKYO KU KYOTO 60601 JAPAN

In order to find a static type system that adequately supports database languages, we need to express the most general type of a program that involves database operations. This can be achieved through an extension to the type system of ML that captures the polymorphic nature of field selection, together with a technique that generalizes relational operators to arbitrary data structures. The combination provides a statically typed language in which generalized relational databases may be cleanly represented as typed structures. As in ML types are inferred, which relieves the programmer of making the type assertions that may be required in a complex database environment. These extensions may also be used to provide static polymorphic typechecking in object-oriented languages and databases. A problem that arises with object-oriented databases is the apparent need for dynamic typechecking when dealing with queries on heterogeneous collections of objects. An extension of the type system needed for generalized relational operations can also be used for manipulating collections of dynamically typed values in a statically typed language. A prototype language based on these ideas has been implemented. While it lacks a proper treatment of persistent data, it demonstrates that a wide variety of database structures can be cleanly represented in a polymorphic programming language.

关键词： theory generalized relational algebra inheritance object-oriented databases polymorphism record calculus type inference

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Incremental materialization of object-oriented views

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DATA & KNOWLEDGE ENGINEERING 1999年第2期29卷 121-145页

作者： Alhajj, R Elnagar, A Sultan Qaboos Univ Dept Comp Sci Muscat Oman

We present an approach to handle incremental materialization of object-oriented views. Queries that define views are implemented as methods that are invoked to compute corresponding views. To avoid computation from scratch each time a view is accessed, we introduce some deferred update algorithms that reflect for a view only related modifications introduced into the database while that view was inactive. A view is updated by considering modifications performed within all classes along the inheritance and class-composition subhierarchies rooted at every class used in deriving that view. To each class, we add a modification list to keep one modification tuple per view dependent on that class. Such a tuple acts as a reference point that marks the start of the next update to the corresponding view. (C) 1999 Elsevier Science B.V. All rights reserved.

关键词： algorithms deferred update incremental update materialized views object-oriented databases

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THE PEGASUS HETEROGENEOUS MULTIDATABASE SYSTEM

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COMPUTER 1991年第12期24卷 19-27页

作者： AHMED, R DESMEDT, P DU, WM KENT, W KETABCHI, MA LITWIN, WA RAFII, A SHAN, MC HEWLETT PACKARD CO PEGASUS PROJECTPALO ALTOCA UNIV PARIS 09 F-75016 PARISFRANCE HEWLETT PACKARD CO PERSEUS PROJECTPALO ALTOCA UNIV SANTA CLARA SCH ENGNSANTA CLARACA 95053

Pegasus, a heterogeneous multidatabase management system that responds to the need for effective access and management of shared data across in a wide range of applications, is described. Pegasus provides facilities for multidatabase applications to access and manipulate multipole autonomous heterogeneous distributed object-oriented relational, and other information systems through a uniform interface. It is a complete data management system that integrates various native and local databases. Pegasus takes advantage of object-oriented data modeling and programming capabilities. It uses both type and function abstractions to deal with mapping and integration problems. Function implementation can be defined in an underlying database language or a programming language. Data abstraction and encapsulation facilities in the Pegasus object model provide an extensible framework for dealing with various kinds of heterogeneities in the traditional database systems and nontraditional data sources

关键词： Pegasus heterogeneous multidatabase system database language distributed databases function abstractions management of shared data object-oriented data modeling object-oriented databases programming language

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On using cache conscious clustering for improving OODBMS performance

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INFORMATION AND SOFTWARE TECHNOLOGY 2006年第11期48卷 1073-1082页

作者： He, Zhen Lai, Richard Marquez, Alonso La Trobe Univ Dept Comp Sci & Comp Engn Melbourne Vic 3086 Australia Australian Natl Univ Dept Comp Sci Canberra ACT 0200 Australia

The two main techniques of improving I/O performance of object oriented Database Management Systems (OODBMS) are clustering and buffer replacement. Clustering is the placement of objects accessed near to each other in time into the same page. Buffer replacement involves the selection of a page to be evicted, when the buffer is full. The page evicted ideally should be the page needed least in the future. These two techniques both influence the likelihood of a requested object being memory resident. We believe an effective way of reducing disk I/O is to take advantage of the synergy that exists between clustering and buffer replacement. Hence, we design a framework, whereby clustering algorithms incorporating buffer replacement cache behaviour can be conveniently employed for enhancing the I/O performance of OODBMS. We call this new type of clustering algorithm, Cache Conscious Clustering (C3). In this paper, we present the C3 framework, and a C3 algorithm that we have developed, namely C3-GP. We have tested C3-GP against three well known clustering algorithms. The results show that C3-GP out performs them by up to 40% when using popular buffer replacement algorithms such as LRU and CLOCK. C3-GP offers the same performance as the best existing clustering algorithm when the buffer size compared to the database size is very small. (C) 2006 Elsevier B.V. All rights reserved.

关键词： object-oriented databases clustering buffer replacement caching database optimisation

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ROVER: flexible yet consistent evolution of relationships

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DATA & KNOWLEDGE ENGINEERING 2001年第1期39卷 27-50页

作者： Claypool, KT Rundensteiner, EA Heineman, GT Worcester Polytech Inst Dept Comp Sci Worcester MA 01609 USA

Relationships have been repeatedly identified as an important object-oriented modeling construct. Most emerging modeling standards such as the object database management group (ODMG) object model and UML have some support for relationships. However object-oriented database (OODB) systems have largely ignored the existence of relationships during schema evolution. We are the first to propose comprehensive support for relationship evolution. A complete schema evolution facility for any OODB system must provide primitives to manipulate all object model constructs, and maintenance strategies for the structural and referential integrity of the database under such evolution. We propose a set of basic evolution primitives for relationships as well as a compound set of changes that can be applied to the same. However, given the myriad of possible change semantics a user may desire in the future, any predefined set is not sufficient. Rather we present a flexible schema evolution framework that allows the user to define new relationship transformations as well as to extend existing ones. Addressing the second problem, namely of updating schema evolution primitives to conform to the new set of invariants, can be a very expensive re-engineering effort. In this paper we present an approach that de-couples the constraints from the schema evolution code, thereby enabling their update without any re-coding effort. We also present an approach that can be used to verify the correctness of these complex evolution operations using the de-coupled constraints. (C) 2001 Published by Elsevier Science B.V.

关键词： schema evolution relationships object-oriented databases consistency management

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A fuzzy knowledge-based system for intelligent retrieval

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IEEE TRANSACTIONS ON FUZZY SYSTEMS 2005年第3期13卷 317-330页

作者： Koyuncu, M Yazici, A Gnkur Mubildeskom TR-06520 Ankara Turkey Middle E Tech Univ Dept Comp Engn TR-06531 Ankara Turkey

For many knowledge-intensive applications, it is important to develop an environment that permits flexible modeling and fuzzy querying of complex data and knowledge including uncertainty. With such an environment, one can have intelligent retrieval of information and knowledge, which has become a critical requirement for those applications. In this paper, we introduce a fuzzy knowledge-based (FKB) system along with the model and the inference mechanism. The inference mechanism is based on the extension of the Rete algorithm to handle fuzziness using a similarity-based approach. The proposed FKB system is used in the intelligent fuzzy object-oriented database (IFOOD) environment, in which a fuzzy object-oriented database is used to handle large scale of complex data while the FKB system is used to handle knowledge of the application domain. Both the fuzzy object-oriented database system and the fuzzy knowledge-based system are based on the object-oriented concepts to eliminate data type mismatches. The aim of this paper is mainly to introduce the FKB system of the IFOOD environment.

关键词： flexible querying fuzzy set theory inference mechanism knowledge-based systems object-oriented databases uncertainty

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Type safety in the context of method updates

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JOURNAL OF INTELLIGENT INFORMATION SYSTEMS 1999年第3期13卷 279-298页

作者： Tari, Z Li, X Liu, L Royal Melbourne Inst Technol Dept Comp Sci Melbourne Vic Australia Univ New S Wales Sch Informat Syst & Management Kensington NSW 2033 Australia Oregon Grad Inst Dept Comp Sci & Engn Portland OR USA

This paper presents a framework for checking and maintaining type safety in the presence of method evolution. A method update often affects all components of the method, including the inter face and the implementation. The type safety problem is addressed as two levels of type consistency. The first level relates to the type checking of methods in the context of the class inheritance hierarchy, and concerns the semantics of the polymorphism of methods. The second level considers the implementation parts of methods by capturing and preserving the semantics of the chain of calling relationships among relevant methods. A graph-based approach is used to achieve this two-level type consistency required at the level of class inheritance hierarchy and the level of method invocation. We demonstrate that the two levels of type consistency checking combined provide a better control of the run-time type error problems.

关键词： object-oriented databases schema update schema consistency type safety

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An object-oriented database system Jasmine: Implementation, application, and extension

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IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING 1996年第2期8卷 285-304页

作者： Ishikawa, H Yamane, Y Izumida, Y Kawato, N FUJITSU LTD NAKAHARA KUKAWASAKIKANAGAWA 211JAPAN

New applications such as engineering tasks require complex object modeling, integration of database and programming facilities, and extensibility. We have devised an object-oriented DBMS called Jasmine for such advanced applications. This paper describes the implementation, application, and extension of Jasmine in detail. First, we focus on the impact of the design of its object-oriented model and language on database implementation technology. We describe what part of traditional relational database technology we extend to handle object-oriented features such as object identifiers, complex objects, class hierarchies, and methods. We introduce nested relations to efficiently store and access clustered complex objects. We use hash-based methods to efficiently access nonclustered complex objects. We provide user-defined functions directly evaluated on page buffers to efficiently process method invocation. We devise object-oriented optimization of queries including class hierarchies, complex objects, and method invocation. We incorporate dedicated object buffering to allow efficient access to objects through object identifiers. Second, we describe nontrivial applications of Jasmine and discuss the validity of object-oriented databases. We focus on a constraint management facility, which can be implemented by taking advantage of the extensibility of Jasmine. The facility includes constraint rules, called design goals, for automatic database population required by engineering applications. Third, we describe a view facility for schema integration also needed by engineering applications in distributed environments. We focus on how we extend Jasmine to implement the facility.

关键词： advanced applications constraint management data model database programming language nested relations object buffering object-oriented databases query language query optimization view mechanism

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