The security problems of object-oriented database system are investigated and security level assignment constraints and an access control mechanism based on the multilevel access control security policy are proposed. ...
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The security problems of object-oriented database system are investigated and security level assignment constraints and an access control mechanism based on the multilevel access control security policy are proposed. The proposed mechanism uses the Trusted Computing Base. A unique feature of the mechanism is that security levels are assigned not only to data items (objects), but also to methods and methods are not shown to the users whose security level is lower than that of the methods. And we distinguish between the security level of a variable in a class and that in an instance and distinguish between the level of an object when it is taken by itself and it is taken as a variable or an element of another complex object. All of this realizes the policy of multilevel access control.
In most object-orienteddatabases, as opposed to value-orienteddatabases, data are accessed by a programming language instead of a declarative query language. End users do not have a simple tool to perform their quer...
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In most object-orienteddatabases, as opposed to value-orienteddatabases, data are accessed by a programming language instead of a declarative query language. End users do not have a simple tool to perform their queries. This paper is concerned with the definition of an SQL-like query language on top of the O2 object-oriented database system. We study the influence of the object-oriented paradigm on a query language, describe our language through examples, define its semantics by means of an algebra and sketch the compilation of RELOOP in one of the languages supported by the O2 system.
A complete framework for enumerating and classifying the types of multidatabasesystem (MDBS) structural and representational discrepancies is developed. The framework is structured according to a relational database ...
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A complete framework for enumerating and classifying the types of multidatabasesystem (MDBS) structural and representational discrepancies is developed. The framework is structured according to a relational database schema and is both practical and complete. It was used to build the UniSQL/M commercial multidatabasesystem. This MDBS was built over Structured-Query-Language-based relational databasesystems and a unified relational and object-oriented database system named UniSQL/X. However, the results are substantially applicable to heterogeneous databasesystems that use a nonrelational data model (for example, an object-oriented data model) as the common data model and allow the formulation of queries directly against the component database schemas
We begin by presenting a descriptive reference model that identifies the important features that need to exist in object query languages. This reference model can be used as a basis for comparing these languages and h...
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We begin by presenting a descriptive reference model that identifies the important features that need to exist in object query languages. This reference model can be used as a basis for comparing these languages and helps provide a foundation for future standardization efforts in this area. We then describe the main features of an object query language that is based on the type system of C++, which we refer to as OQL[C++]. A query module based on OQL[C++] is being developed as part of the Zeitgeist OODB project at Texas Instruments. OQL[C++] extends the C++ programming language by providing support for managing and associatively querying sets of objects in a C++ program. OQL[C++] queries are orthogonal to persistence in the sense that they can be issued against persistent as well as transient sets of objects. The proposed OQL[C++], provides an evolutionary path from the industry's standard query language SQL to an object query language. Using ideas similar to those presented in this paper, one can propose OQL[X] where X is either an object data model, or the type system of an object-oriented programming language such as CLOS or object Pascal.
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.
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]
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