In a federated database environment, different constituents of the federation may use different temporal models or physical representations for temporal information. This paper introduces a new concept, called a tempo...
ISBN:
(纸本)9780897915922
In a federated database environment, different constituents of the federation may use different temporal models or physical representations for temporal information. This paper introduces a new concept, called a temporal module, to resolve these differences, or mismatches, among the constituents. Intuitively, a temporal module hides the implementation details of a temporal relation by exposing its information only through two windowing functions: The first function associates each time point with a set of tuples and the second function links each tuple to a set of time points. A calculus-style language is given to form queries on temporal *** modules are then extended to resolve another type of mismatch among the constituents of a federation, namely, the mismatch involving different time units (e.g., month, week and day) used to record temporal information. Our solution relies on “information conversions” provided by each constituent. Specifically, each temporal module is extended to provide several “windows” to its information, each in terms of a different time unit. The first step to process a query addressed to the federation is to select suitable windows to the underlying temporal modules. In order to facilitate such a process, time units are formally defined and studied. A federated temporal database model and its query language are proposed. The query language is an extension of the above calculus-style language.
The introduction and use of formal (mathematically based) specification in substantial systems development has been hampered by the additional burdens it places on practitioners. BT and Leeds Metropolitan University, ...
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The concurrency control protocol that has been implemented in the commercially available Trusted Oracle multilevel secure database management system (DBMS) generates histories that are level-wise serializable. Level-w...
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The concurrency control protocol that has been implemented in the commercially available Trusted Oracle multilevel secure database management system (DBMS) generates histories that are level-wise serializable. Level-wise serializability suffers from the inconsistent retrieval problems which may seriously harm database integrity. The authors show that it is possible to meet stricter correctness criteria using Trusted Oracle, provided knowledge of the update transactions that will be executed in the system is available. They perform a static analysis of the read- and write-sets of these transactions and, based on this analysis, control the order of submission of the transactions to the scheduler in such a way that the resultant history ensures higher correctness level. The exact order chosen depends on the level of consistency desired. The goal is achieved without modifying the Trusted Oracle concurrency control algorithm in any way.< >
This article discusses data security and controls, primarily in the context of data base management systems (DBMSs), with an emphasis on basic principles and mechanisms that have been successfully used by practitioner...
In a federated database environment, different constituents of the federation may use different temporal models or physical representations for temporal information. This paper introduces a new concept, called a tempo...
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作者：
Bex, H.Greuel, K.Prof. Dr.-Ing. Hans Bex (1937)
VDE VDI IEEE is head of the department of High-Frequency Techniques at the Fachhochschule of Aachen Germany. He received his degrees at the Technical University of Aachen Germany in 1965 and 1969. From 1965 to 1980 he was with the Philips Research Laboratories in Aachen as a research scientist where he was engaged in research on lumped element circulators YIG-filters linear and non-linear microstrip circuits for microwave subsystems. Since 1981 he has been a professor for high-frequency techniques at the Fachhoch-schule Aachen Germany teaching electromagnetics and microwaves. His areas of interest include microwave and millimeter wave integrated circuits and devices non-linear analysis techniques device modelling planar transmission line modelling and electromagnetic field theory applied to isotropic and anisotropic materials. (FH Aachen Abteilung fur Theoretische Nachrichtentechnik und Hochstfrequenztechnik. Eupener Str. 70 D-52066 Aachen T + 492 41/60 09 21 08 Fax + 49 241/60 09 21 91) Dipl.-Ing. Karl Greuel (1960)
VDE studied Electrical Engineering at the FH Aachen Germany and got his degree there in 1988. After his study he designed software for industry-furnaces with stored-program controllers at the Otto Junker GmbH. Since 1990 he works at the Datus GmbH for electrical information-systems in software development. (Datus GmbH Abteilung Software-Entwicklung Tempelhofer Str. 4-6 D-52068 Aachen T +49241/1 6802-0 Fax + 492 41/168 02-80)
In this paper inductive melting in a metal sphere is investigated, whereby the temperature dependence of the sample 's most important material parameters is considered. The solid‐liquid interface in the sphere is...
In the schematic protection model subjects are classified into protection types. Creation is authorized by a can-create binary relation on types. It is shown that with arbitrary cycles in can-create safety is undecida...
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In the schematic protection model subjects are classified into protection types. Creation is authorized by a can-create binary relation on types. It is shown that with arbitrary cycles in can-create safety is undecidable. Whereas it has been previously shown safety is decidable for acyclic can-create. It is also shown that safety remains undedicable even if all creates are attenuating in that tickets (capabilities) given to a subject on its creation are attenuated copies of tickets available to its parent. This contrasts with decidable safety for attenuating cycles of length one. It appears safety is decidable for the practically useful cases while undecidability results from undue laxity in authorizing creation.
Several institutions in industry and academia are pursuing research efforts in domain modeling to address unresolved issues in software reuse. To demonstrate the concepts of domain modeling and software reuse, a proto...
Access control models provide a formalism and framework for specifying control over access to information and other resources in multi-user computer systems. Useful access control models must balance expressive power ...
Polyinstantiation has generated a great deal of controversy lately. Some have argued that polyinstantiation and integrity are fundamentally incompatible, and have proposed alternatives to polyinstantiation. Others hav...
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