Integrity Control in Relational Database Systems - An Overview

This paper gives an overview of research regarding integrity control or integrity constraint handling in relational database management systems. The topic of constraint handling is discussed from two points of view. First, constraint handling is discussed by identifying a number of important research issues, and by treating each issue in detail. Second, a number of projects is described that have resulted in the realization of database management systems supporting integrity constraints; the various projects are compared with respect to a number of system characteristics. Together, both approaches give a broad overview of the state of the art in the field at this moment

Optimiser-based recommendations of physical database design

Die Komplexitiät aktueller relationaler Datenbank Management Systeme stellt eine immer größere Herausforderung an Datenbankadministratoren dar. Jede Laufzeitumgebung benötigt eine für sie angepasste Konfiguration, um performant zu operieren. Selbst innerhalb einer Umgebung können sich die Anforderungen im Laufe der Zeit ändern und eine erneute Anpassung erfordern. Dies zwingt den DBA sich kontinuierlich und intensiv mit dem System zu beschäftigen. Das Ziel eines modernen DBMS muss die Unterstützung des DBAs sein, um seine Arbeit mit automatisierten Prozessen und Handlungsabläufen zu erleichtern und ihm so stets schnelle und prezise Entscheidungen zu ermöglichen. Diese Arbeit zielt auf die Beschreibung und teilweise Umsetzung eines unterstützenden Systems, das die aktuelle DBMS Konfiguration zusammen mit dem aktuellen Anfrageverhalten analysiert und dem DBA Vorschläge unterbreitet, wie sich die Performanz und Effizienz des Systems verbessern lässt.Today's relational database management systems are made up of many complex components and managing these presents a growing challenge for database administrators. Every runtime environment can require different configurations to deliver adequate performance. Even withinthe same environment demands can shift over time when workloads change. Keeping up with these demands requires continuous effort from the DBA. The goal of a modern DBMS must be to support the DBA in his work with automated processes and workflows that allow him tomake quick and precise decisions. This work aims at describing and partially implementing asupportive system that will analyse the current DBMS configuration together with its workload to give recommendations on how to improve its performance and efficiency.Ilmenau, Techn. Univ., Diplomarbeit, 200

Database rules and time: some proposed extensions to the SQL standard

The subject of this thesis is the incorporation of temporal semantics into database rules and how the resultant syntax might be reconciled with the evolving SQL standard. In particular, it explores time-driven rules and the time-relationship between triggering events and associated actions. A review of the key research results in the area of database rules and the syntax developed for the major prototype implementations is conducted, and a working syntax , free of any limitations within the SQL standard, developed. Next, an operational definition is evolved through the application of this working syntax to two sample domains rich in 'temporal rules'. In each case a graphical representation of the domain is presented using an adapted object-oriented modelling technique followed by a mapping into the working temporal syntax. Attention is then turned to the SQL-92 standard and its future successor SQL3. An assessment is made of their implications for the working syntax developed in the earlier chapters - with particular reference to the specification of time and the use of database triggers. When an attempt was made to re-cast the working syntax into SQL, a satisfactory mapping, which succeeded in preserving the semantics of the original, could not be achieved. Support for time-based triggers; cyclic operations; delayed actions and rule lifetimes necessitated the development of appropriate modifications to the basic SQL3 draft syntax. The proposed extensions capture all of the semantics required for the specification of time-based rules. The example applications indicated that an extended SQLcompliant language approach allied to a sound objectoriented modelling formalism had a broad applicability. Furthermore, it was apparent that the addition of a temporal dimension to rule actions was a key enabling factor in increasing their semantic power

Towards an Efficient Evaluation of General Queries

Database applications often require to evaluate queries containing quantifiers or disjunctions, e.g., for handling general integrity constraints. Existing efficient methods for processing quantifiers depart from the relational model as they rely on non-algebraic procedures. Looking at quantified query evaluation from a new angle, we propose an approach to process quantifiers that makes use of relational algebra operators only. Our approach performs in two phases. The first phase normalizes the queries producing a canonical form. This form permits to improve the translation into relational algebra performed during the second phase. The improved translation relies on a new operator - the complement-join - that generalizes the set difference, on algebraic expressions of universal quantifiers that avoid the expensive division operator in many cases, and on a special processing of disjunctions by means of constrained outer-joins. Our method achieves an efficiency at least comparable with that of previous proposals, better in most cases. Furthermore, it is considerably simpler to implement as it completely relies on relational data structures and operators

Forensic attribution challenges during forensic examinations of databases

An aspect of database forensics that has not yet received much attention in the academic research community is the attribution of actions performed in a database. When forensic attribution is performed for actions executed in computer systems, it is necessary to avoid incorrectly attributing actions to processes or actors. This is because the outcome of forensic attribution may be used to determine civil or criminal liability. Therefore, correctness is extremely important when attributing actions in computer systems, also when performing forensic attribution in databases. Any circumstances that can compromise the correctness of the attribution results need to be identified and addressed. This dissertation explores possible challenges when performing forensic attribution in databases. What can prevent the correct attribution of actions performed in a database? Thirst identified challenge is the database trigger, which has not yet been studied in the context of forensic examinations. Therefore, the dissertation investigates the impact of database triggers on forensic examinations by examining two sub questions. Firstly, could triggers due to their nature, combined with the way databases are forensically acquired and analysed, lead to the contamination of the data that is being analysed? Secondly, can the current attribution process correctly identify which party is responsible for which changes in a database where triggers are used to create and maintain data? The second identified challenge is the lack of access and audit information in NoSQL databases. The dissertation thus investigates how the availability of access control and logging features in databases impacts forensic attribution. The database triggers, as dened in the SQL standard, are studied together with a number of database trigger implementations. This is done in order to establish, which aspects of a database trigger may have an impact on digital forensic acquisition, analysis and interpretation. Forensic examinations of relational and NoSQL databases are evaluated to determine what challenges the presence of database triggers pose. A number of NoSQL databases are then studied to determine the availability of access control and logging features. This is done because these features leave valuable traces for the forensic attribution process. An algorithm is devised, which provides a simple test to determine if database triggers played any part in the generation or manipulation of data in a specific database object. If the test result is positive, the actions performed by the implicated triggers will have to be considered in a forensic examination. This dissertation identified a group of database triggers, classified as non-data triggers, which have the potential to contaminate the data in popular relational databases by inconspicuous operations, such as connection or shutdown. It also established that database triggers can influence the normal ow of data operations. This means what the original operation intended to do, and what actually happened, are not necessarily the same. Therefore, the attribution of these operations becomes problematic and incorrect deductions can be made. Accordingly, forensic processes need to be extended to include the handling and analysis of all database triggers. This enables safer acquisition and analysis of databases and more accurate attribution of actions performed in databases. This dissertation also established that popular NoSQL databases either lack sufficient access control and logging capabilities or do not enable them by default to support attribution to the same level as in relational databases.Dissertation (MSc)--University of Pretoria, 2018.Computer ScienceMScUnrestricte

Three Denerations of DBMS

This paper describes the evolution of data base technology from early computing to the sophisticated systems of today. It presents an overview of the most popular data base management systems architectures such as hierarchical, network, relational and object-oriented. The last section of this paper presents a view of the factors that will influence the future of data base technology

Design exploration through bidirectional modeling of constraints

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Architecture, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 315-324).Today digital models for design exploration are not used to their full potential. The research efforts in the past decades have placed geometric design representations firmly at the center of digital design environments. In this thesis it is argued that models for design exploration that bridge different representation aid in the discovery of novel designs. Replacing commonly used analytical, uni-directional models for linking representations, with bidirectional ones, further supports design exploration. The key benefit of bidirectional models is the ability to swap the role of driver and driven in the exploration. The thesis developed around a set of design experiments that tested the integration of bidirectional computational models in domain specific designs. From the experiments three main exploration types emerged. They are: branching explorations for establishing constraints for an undefined design problem; illustrated in the design of a concept car. Circular explorations for the refinement of constraint relationships; illustrated in the design of a chair. Parallel explorations for exercising well-understood constraints; illustrated in a form finding model in architecture. A key contribution of the thesis is the novel use of constraint diagrams developed to construct design explorers for the experiments. The diagrams show the importance of translations between design representations in establishing design drivers from the set of constraints. The incomplete mapping of design features across different representations requires the redescription of the design for each translation.(cont.) This redescription is a key aspect of exploration and supports design innovation. Finally, this thesis argues that the development of design specific design explorers favors a shift in software design away from monolithic, integrated software environments and towards open software platforms that support user development.by Axel Kilian.Ph.D

Database system architecture supporting coexisting query languages and data models

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