In this paper we describe multilevel security issues for hypermedia-based information retrieval database management systems. We first summarize the discussion in our earlier paper on the use of object-oriented approac...
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In this paper we describe multilevel security issues for hypermedia-based information retrieval database management systems. We first summarize the discussion in our earlier paper on the use of object-oriented approach for developing secure information retrieval systems and then discuss in detail how such a system can be augmented by a Linker to provide hypermedia database management system capabilities. In particular, we discuss various types of nodes and links, an architecture for a hypermedia-based information retrieval system, the various functions of such a system including information retrieval, browsing and update operations, and the interface to the underlying multilevel secure information retrieval system. Finally, the concepts are illustrated using an example.
Views are an important functionality provided by the relational databasesystems. However, commercial object-oriented database systems do not support a view mechanism because defining the semantics of views in the con...
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Views are an important functionality provided by the relational databasesystems. However, commercial object-oriented database systems do not support a view mechanism because defining the semantics of views in the context of an object-oriented model is more difficult than in the relational model. Indeed, views are not included in the ODMG standard. In this paper, we present a proposal aimed at including views in the ODMG, by extending the object model and the object definition language (ODL). We consider object-oriented views as having the same functionality as relational views. Views are included in the object model in such a way that (i) views make a new kind of data type definition, just as are classes, interfaces and literals, (ii) an IS-VIEW relationship is introduced in order to specify the derivation of a view from its base class, and (iii) a view instance preserves the identity of its base instance. A view can import attributes, relationships and operations from its base class, and it can also add new operations, derived attributes and derived relationships. The extent of the view is defined by an object query language (OQL) predicate. We also describe a C++ binding showing the practicability of the proposed model. (C) 2002 Elsevier Science B.V. All rights reserved.
The PROBE research project has produced results in the areas of data modeling, spatial/temporal query processing, recursive query processing, and databasesystem architecture for 'nontraditional' application a...
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The PROBE research project has produced results in the areas of data modeling, spatial/temporal query processing, recursive query processing, and databasesystem architecture for 'nontraditional' application areas, many of which involve spatial data and data with complex structure. PROBE provides the point set as a construct for modeling spatial data. This abstraction is compatible with notions of spatial data found in a wide variety of applications. PROBE is extensible and supports a generalization hierarchy, so it is possible to incorporate application-specific implementations of the point set abstraction. PROBE's query processor supports point sets with the geometry filter, an optimizer of spatial queries. Spatial queries are processed by decomposing them into 1) a set-at-a-time portion that is evaluated efficiently by the geometry filter and 2) a portion that involves detailed manipulations of individual spatial objects by functions supplied with the application-specific representation. The output from the first step is an approximate answer, which is refined in the second step. The data model and the geometry filter are valid in all dimensions, and they are compatible with a wide variety of representations. PROBE's spatial data model and geometry filter are described, and it is shown how these facilities can be used to support image database applications. [ABSTRACT FROM AUTHOR]
This paper describes a technique to implement an object-oriented functional data model that optimizes performance for a given set of applications (workload). The technique involves grouping functions that are often re...
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This paper describes a technique to implement an object-oriented functional data model that optimizes performance for a given set of applications (workload). The technique involves grouping functions that are often referenced together or that are often composed. These groups are referred to as access trees which may be considered as abstract storage structures. The focus of this paper is the design of a set of access trees (called the cover) for a given conceptual schema so that the cost of processing the workload is as low as possible and the space of the cover is within some user-specified limit. It is found that using this implementation scheme, a significant reduction in access time is obtainable at the cost of a tolerable space increment. The paper describes the conceptual data model, the structure and use of access trees, an implementation of access trees, costs associated with operations on the access trees, and a methodology to design the optimal set of access trees for a conceptual schema with respect to a given workload. An experimental analysis of the performance of the technique is presented.
This paper discusses the concurrency control of the object-oriented database system (OODBS), and presents a simulation model for the following basic elements which should be considered from the viewpoint of the data s...
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This paper discusses the concurrency control of the object-oriented database system (OODBS), and presents a simulation model for the following basic elements which should be considered from the viewpoint of the data structure: (1) the entity should be modeled, based on the concept of object;(2) the definition of the attribute and the method should be inherited based on the class hierarchy;and (3) the composite object should be realized. Based on this model, performance evaluations are conducted on Two-Phase Locking protocol (2PL) and Conflict-Preserving Serializable scheduler (CPS). From investigations, so far, on the flat structure, CPS has shown better performance than 2PL. As a result of this study, however, it is shown that in the prominent data structure of OODBS, there exist access conflicts where the optimistic concurrency control such as CPS works effectively, as well as access conflicts where the pessimistic concurrency control such as 2PL works effectively.
With recent spread of network environments, exchange of diverse and voluminous data between computers gains increasing importance. Abstract Syntax Notation One (ASN.1) was proposed as a language to define data structu...
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