Browsing by Subject "Database management."

Now showing 1 - 10 of 10

Open Access
A database for evaluating stocks trading in ISE
(1994) Kaya, Arda
This thesis is a design of a database that will store and manage the data of Istanbul Stock Exchange. The system is capable of storing the data of all companies for the time periods defined, adjusting price data to normalize capital increase and dividend effects, and producing custom designed reports to provide users flexibility. The program, which provides interface to database, is menu driven and user friendly.
Open Access
Development and evaluation of inter-query optimization heuristics in database systems
(1996) Kulabaş, Yiğit
In a multi-user database system multiple queries can be issued by different users at about the same time. These queries may have some common operations and/or common relations to process. In our work, we have developed some inter-query optimization heuristics for improving the performance by exploiting the common relations within the queries. We have focused mostly on the join operation, with the build and probe phases. Some of the proposed heuristics are for the build phase, some for the probe phase, and finally some for the memory flush operation. The performance of the proposed heuristics is studied using a simple simulation model. We show that the heuristics can provide significant performance improvements compared to conventional scheduling methods for different workloads.
Open Access
An extended relational algebra for nested relations
(1993) Sükan, Eser
In this study the database models of Roth-Korth-Silberschatz (RKS) [cf. ACM TODS 13(4): 389—417, 1988] and Abiteboul-Bidoit (AB) [cf. Journal of Computer and System Sciences 33(4): 361—393, 1986] to formalize non-firstnormal-form relations are presented along with their extended relational algebra. We show that the extended set operators union and difference of RKS and AB are not information equivalent Using the model of RKS and restricting ourselves to union and difference, we define our extended set operators and show that these two operators and the extended intersection of RKS are information equivalent.
Open Access
Image searching with signature filtering and multidimensional indexing
(1997) Günyaktı, Çağlar
Open Access
An implementation of a temporal relational database management system
(1992) Goralwalla, Iqbal A.
111 this work, the implementation of a temporal database management system is reported. This system has been implemented on top of an existing database system that manipulates relations with set-valued attributes. The temporal relational model together with the tem])oral algebra are descril)ed. The basic set of opercitions of the extended relational algebra have been modified to handle temporal attributes. New operations have been added to help in the extraction of information from historical relations. These operations convcirt one attrilnite type to another and do selection over the time'dimension. Moreover, a statistical interface has been added to the system. This interface includes aggregate functions and a new operation, enumeration^ which derives a table of uniform data for a set of time points or intervals, from a three dimensional historical relation. A performance evaluation of the system is carried out by executing sample queries against different types of databases: snapshot, snapshot/nested and historical.
Open Access
Implementation of parallel nested transactions for nested rule execution in active databases
(1996) Saygın, Yücel
(Jonventional, passive datal)ases, ex('cute transcictions or queries in response to the requests from a user or an application program. In contrcist, an Active Database Management System (ADI3MS) allows users to specify actions to be executed when some specific evcMits are signaled. ADBMSs ¿ichieve tliis feciture by mecins of rules. Execution of ruh's is an important part of an ADBMS which may affect the overall performanc'e of the system. Nested transactions are proposed as a rule execution model for ADBMSs. The nested trcinsciction model, in contrast to flat transactions, allows transactions to be started inside some other trcinsactions forming a transaction hierarchy. In this thesis, implementation issues of pcirallel nested transactions, wluM’e all the transactions in the hierarchy may run in pcirallel, aix' discussed for parallel rule execution in ADBMSs. Implementation of nested transactions ha.s I^een performed by extending the flat trcuisaction semantics of OpenOODB using Solaris threads. A formal specification of the proposed (xxec.ution model using ACTA framework is also provided.
Open Access
Metadata-based and personalized web querying
(2004) Özel, Selma Ayşe
The advent of the Web has raised new searching and querying problems. Keyword matching based querying techniques that have been widely used by search engines, return thousands of Web documents for a single query, and most of these documents are generally unrelated to the users’ information needs. Towards the goal of improving the information search needs of Web users, a recent promising approach is to index the Web by using metadata and annotations. In this thesis, we model and query Web-based information resources using metadata for improved Web searching capabilities. Employing metadata for querying the Web increases the precision of the query outputs by returning semantically more meaningful results. Our Web data model, named “Web information space model”, consists of Web-based information resources (HTML/XML documents on the Web), expert advice repositories (domain-expert-specified metadata for information resources), and personalized information about users (captured as user profiles that indicate users’ preferences about experts as well as users’ knowledge about topics). Expert advice is specified using topics and relationships among topics (i.e., metalinks), along the lines of recently proposed topic maps standard. Topics and metalinks constitute metadata that describe the contents of the underlying Web information resources. Experts assign scores to topics, metalinks, and information resources to represent the “importance” of them. User profiles store users’ preferences and navigational history information about the information resources that the user visits. User preferences, knowledge level on topics, and history information are used for personalizing the Web search, and improving the precision of the results returned to the user. We store expert advices and user profiles in an object relational database iv v management system, and extend the SQL for efficient querying of Web-based information resources through the Web information space model. SQL extensions include the clauses for propagating input importance scores to output tuples, the clause that specifies query stopping condition, and new operators (i.e., text similarity based selection, text similarity based join, and topic closure). Importance score propagation and query stopping condition allow ranking of query outputs, and limiting the output size. Text similarity based operators and topic closure operator support sophisticated querying facilities. We develop a new algebra called Sideway Value generating Algebra (SVA) to process these SQL extensions. We also propose evaluation algorithms for the text similarity based SVA directional join operator, and report experimental results on the performance of the operator. We demonstrate experimentally the effectiveness of metadata-based personalized Web search through SQL extensions over the Web information space model against keyword matching based Web search techniques.
Open Access
Objective: a benchmark for object-oriented active database systems
(1996) Çetintemel, Uğur
Although much work in the area of Active Database Management Systems (ADBMSs) has been done, there have been only a few attempts to evaluate the performance of these systems, and it is not yet clear how the performance of an active DBMS can be evaluated systematically. In this thesis, we describe the OBJECTIVE Benchmark for object-oriented ADBMSs, and present experimental results from its implementation in an active database system prototype. OBJECTIVE can be used to identify performance bottlenecks and active functionalities of an ADBMS, and compare the performance of multiple ADBMSs. The philosophy of OBJECTIVE is to isolate components providing active functionalities, and concentrate only on the performance of these components while attempting to minimize the effects of other factors.
Open Access
Storage management and indexing in object-oriented database management systems
(1990) Al-Hajj, Reda
Storage management and indexing methods used in existing conventional database management systems are not appropriate for the object-oriented database management systems due to the distinctive features of the later systems. A model for storage management suitable for object- oriented database management systems is proposed in this thesis. It supports object identity, multiple inheritance, composite objects, a fine degree of granularity and schema evolution. An index provides fast access to data stored in files at the price of using additional storage space and an overhead in update operations. Work has been carried out on indexing and an indexing method for the object-oriented database systems is proposed. Identity and equality indexes are treated. Object identity and information hiding are provided. Schema changes are handled without affecting existing indexes. It is general enough to be applicable to most existing object-oriented database systems. The mapping of the proposed storage and indexing approaches into a relational database scheme is also presented.
Open Access
Transaction execution in multidatabase systems
(1996) Devirmiş, Timuçin
Most work in the multiclatabase systems (MDBSs) area has focused on the issues of transaction management and concurrency control. It is difficult to implement traditional transaction management techniques in a MDBS due to the heterogeneity and autonomy of the connected local sites. In this thesis, we present a new transaction execution model that captures the formalism and semantics of various extended transaction models and adopts them to a MDBS environment. The proposed model covers nested transactions, various dejjendenc}' types among subtransactions, and commit-independent transactions. The execution model does not make any assumption regarding the concurrency control protocols executed at the local sites connected to the MDBS. VVe also present a detailed simulation model of a MDBS to aiiiilyze the performance of the proposed model. The performances of both the traditional transaction model and the proposed transaction model are evaluated under a range of workloads and system configurations. The performance impact of global transactions’ behavior on local transactions is also discussed.