by Frank Hing-Wah Luk. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 92-95). / Abstract --- p.ii / Acknowledgement --- p.iii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation --- p.1 / Chapter 1.2 --- The Problem in Object-Oriented Database Indexing --- p.2 / Chapter 1.3 --- Contributions --- p.3 / Chapter 1.4 --- Thesis Organization --- p.4 / Chapter 2 --- Object-oriented Data Model --- p.5 / Chapter 2.1 --- Object-oriented Data Model --- p.5 / Chapter 2.2 --- Object and Object Identifiers --- p.6 / Chapter 2.3 --- Complex Attributes and Methods --- p.6 / Chapter 2.4 --- Class --- p.8 / Chapter 2.4.1 --- Inheritance Hierarchy --- p.8 / Chapter 2.4.2 --- Aggregation Hierarchy --- p.8 / Chapter 2.5 --- Sample Object-Oriented Database Schema --- p.9 / Chapter 3 --- Indexing in Object-Oriented Databases --- p.10 / Chapter 3.1 --- Introduction --- p.10 / Chapter 3.2 --- Indexing on Inheritance Hierarchy --- p.10 / Chapter 3.3 --- Indexing on Aggregation Hierarchy --- p.13 / Chapter 3.4 --- Indexing on Integrated Support --- p.16 / Chapter 3.5 --- Indexing on Method Invocation --- p.18 / Chapter 3.6 --- Indexing on Overlapping Path Expressions --- p.19 / Chapter 4 --- Triple Node Hierarchy --- p.23 / Chapter 4.1 --- Introduction --- p.23 / Chapter 4.2 --- Triple Node --- p.25 / Chapter 4.3 --- Triple Node Hierarchy --- p.26 / Chapter 4.3.1 --- Construction of the Triple Node Hierarchy --- p.26 / Chapter 4.3.2 --- Updates in the Triple Node Hierarchy --- p.31 / Chapter 4.4 --- Cost Model --- p.33 / Chapter 4.4.1 --- Storage --- p.33 / Chapter 4.4.2 --- Query Cost --- p.35 / Chapter 4.4.3 --- Update Cost --- p.35 / Chapter 4.5 --- Evaluation --- p.37 / Chapter 4.6 --- Summary --- p.42 / Chapter 5 --- Triple Node Hierarchy in Both Aggregation and Inheritance Hierarchies --- p.43 / Chapter 5.1 --- Introduction --- p.43 / Chapter 5.2 --- Preliminaries --- p.44 / Chapter 5.3 --- Class-Hierarchy Tree --- p.45 / Chapter 5.4 --- The Nested CH-tree --- p.47 / Chapter 5.4.1 --- Construction --- p.47 / Chapter 5.4.2 --- Retrieval --- p.48 / Chapter 5.4.3 --- Update --- p.48 / Chapter 5.5 --- Cost Model --- p.49 / Chapter 5.5.1 --- Assumptions --- p.51 / Chapter 5.5.2 --- Storage --- p.52 / Chapter 5.5.3 --- Query Cost --- p.52 / Chapter 5.5.4 --- Update Cost --- p.53 / Chapter 5.6 --- Evaluation --- p.55 / Chapter 5.6.1 --- Storage Cost --- p.55 / Chapter 5.6.2 --- Query Cost --- p.57 / Chapter 5.6.3 --- Update Cost --- p.62 / Chapter 5.7 --- Summary --- p.63 / Chapter 6 --- Decomposition of Path Expressions --- p.65 / Chapter 6.1 --- Introduction --- p.65 / Chapter 6.2 --- Configuration on Path Expressions --- p.67 / Chapter 6.2.1 --- Single Path Expression --- p.67 / Chapter 6.2.2 --- Overlapping Path Expressions --- p.68 / Chapter 6.3 --- New Algorithm --- p.70 / Chapter 6.3.1 --- Example --- p.72 / Chapter 6.4 --- Evaluation --- p.75 / Chapter 6.5 --- Summary --- p.76 / Chapter 7 --- Conclusion and Future Research --- p.77 / Chapter 7.1 --- Conclusion --- p.77 / Chapter 7.2 --- Future Research --- p.78 / Chapter A --- Evaluation of some Parameters in Chapter5 --- p.79 / Chapter B --- Cost Model for Nested-Inherited Index --- p.82 / Chapter B.1 --- Storage --- p.82 / Chapter B.2 --- Query Cost --- p.84 / Chapter B.3 --- Update --- p.84 / Chapter C --- Algorithm constructing a minimum auxiliary set of J Is --- p.87 / Chapter D --- Estimation on the number of possible combinations --- p.89 / Bibliography --- p.92

Typescript, etc. / Digitized by Kansas Correctional Industries

Typescript, etc. / Digitized by Kansas Correctional Industries

Main subjects of this thesis are distant learning and e-learning. It provides an overview of current state of distance learning in tertiary education in Czech republic, focusing mainly on informatics programs. It identifies limitations of standard e-learning systems regarding the requirements of courses on the Faculty of Informatics and Statistics at University of Economics, Prague. Practical part of this thesis is describing implementation and use of special application that provides functionality that is not provided by standard e-learning systems.

The focus of this thesis is on systems that employ both flash and magnetic disks as storage media. Considering the widely disparate I/O costs of flash disks currently on the market, our approach is a cost-aware one: we explore techniques that exploit the I/O costs of the underlying storage devices to improve I/O performance. We also study the asymmetric I/O properties of magnetic and flash disks and propose algorithms that take advantage of this asymmetry. Our work is geared towards database systems; however, most of the ideas presented in this thesis can be generalised to any data-intensive application. For the case of low-end, inexpensive flash devices with large capacities, we propose using them at the same level of the memory hierarchy as magnetic disks. In such setups, we study the problem of data placement, that is, on which type of storage medium each data page should be stored. We present a family of online algorithms that can be used to dynamically decide the optimal placement of each page. Our algorithms adapt to changing workloads for maximum I/O efficiency. We found that substantial performance benefits can be gained with such a design, especially for queries touching large sets of pages with read-intensive workloads. Moving one level higher in the storage hierarchy, we study the problem of buffer allocation in databases that store data across multiple storage devices. We present our novel approach to per-device memory allocation, under which both the I/O costs of the storage devices and the cache behaviour of the data stored on each medium determine the size of the main memory buffers that will be allocated to each device. Towards informed decisions, we found that the ability to predict the cache behaviour of devices under various cache sizes is of paramount importance. In light of this, we study the problem of efficiently tracking the hit ratio curve for each device and introduce a lowoverhead technique that provides high accuracy. The price and performance characteristics of high-end flash disks make them perfectly suitable for use as caches between the main memory and the magnetic disk(s) of a storage system. In this context, we primarily focus on the problem of deciding which data should be placed in the flash cache of a system: how the data flows from one level of the memory hierarchy to the others is crucial for the performance of such a system. Considering such decisions, we found that the I/O costs of the flash cache play a major role. We also study several implementation issues such as the optimal size of flash pages and the properties of the page directory of a flash cache. Finally, we explore sorting in external memory using external merge-sort, as the latter employs access patterns that can take full advantage of the I/O characteristics of flash memory. We study the problem of sorting hierarchical data, as such is necessary for a wide variety of applications including archiving scientific data and dealing with large XML datasets. The proposed algorithm efficiently exploits the hierarchical structure in order to minimize the number of disk accesses and optimise the utilization of available memory. Our proposals are not specific to sorting over flash memory: the presented techniques are highly efficient over magnetic disks as well.

Deng, Hongbo. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 156-175). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Database management is a very important subject in computer science education. The study of SQL syntax is the most important part of this course. The traditional teaching method only lets the students practice SQL syntax through the textbook exercise. Students cannot get the query result directly. Moreover, students do not know intuitively what is wrong with the query sentence. In this study, we want to find a better way for the teachers and the students to learn this part of database management. Teacher uploads a SQL file through a web page, it will create a database with several tables and some data records on the database server. The student logs in to the platform and chooses the database that he wants to practice. The student can do all regular database management operations such as query data, insert data, delete data, etc. If the query sentence is correct, the query result will be displayed on the webpage. If not, the detailed error information will show up. Since there is more than one student using the platform, so these operations cannot change the database created by the teacher. Therefore, the student’s process will run in a Docker container. In the container, there is a duplicated database of the teacher’s database. Meanwhile, the platform supports multiple users to do exercise with one database at the same time.

No description available.

Browsing marked-up documents by traversing hyperlinks has become probably the most important means by which documents are accessed, both via the World Wide Web (WWW) and organisational Intranets. However, there is a pressing demand for document management and retrieval systems to deal appropriately with the massive number of documents available. There are two classes of solution: general search engines, whether for the WWW or an Intranet, which make little use of specific domain knowledge or hand-crafted specialised systems which are costly to build and maintain. The aim of this thesis was to develop a document management and retrieval system suitable for small communities as well as individuals in specialised domains on the Web. The aim was to allow users to easily create and maintain their own organisation of documents while ensuring continual improvement in the retrieval performance of the system as it evolves. The system developed is based on the free annotation of documents by users and is browsed using the concept lattice of Formal Concept Analysis (FCA). A number of annotation support tools were developed to aid the annotation process so that a suitable system evolved. Experiments were conducted in using the system to assist in finding staff and student home pages at the School of Computer Science and Engineering, University of New South Wales. Results indicated that the annotation tools provided a good level of assistance so that documents were easily organised and a lattice-based browsing structure that evolves in an ad hoc fashion provided good efficiency in retrieval performance. An interesting result suggested that although an established external taxonomy can be useful in proposing annotation terms, users appear to be very selective in their use of terms proposed. Results also supported the hypothesis that the concept lattice of FCA helped take users beyond a narrow search to find other useful documents. In general, lattice-based browsing was considered as a more helpful method than Boolean queries or hierarchical browsing for searching a specialised domain. We conclude that the concept lattice of Formal Concept Analysis, supported by annotation techniques is a useful way of supporting the flexible open management of documents required by individuals, small communities and in specialised domains. It seems likely that this approach can be readily integrated with other developments such as further improvements in search engines and the use of semantically marked-up documents, and provide a unique advantage in supporting autonomous management of documents by individuals and groups - in a way that is closely aligned with the autonomy of the WWW.

The term quote semantic query optimization quote (SQO) denotes a methodology whereby queries against databases are optimized using semantic information about the database objects being queried. The result of semantically optimizing a query is another query which is syntactically different to the original, but semantically equivalent and which may be answered more efficiently than the original. SQO is distinctly different from the work performed by the conventional SQL optimizer. The SQL optimizer generates a set of logically equivalent alternative execution paths based ultimately on the rules of relational algebra. However, only a small proportion of the readily available semantic information is utilised by current SQL optimizers. Researchers in SQO agree that SQO can be very effective. However, after some twenty years of research into SQO, there is still no commercial implementation. In this thesis we argue that we need to quantify the conditions for which SQO is worthwhile. We investigate what these conditions are and apply this knowledge to relational database management systems (RDBMS) with static schemas and infrequently updated data. Any semantic query optimizer requires the ability to reason using the semantic information available, in order to draw conclusions which ultimately facilitate the recasting of the original query into a form which can be answered more efficiently. This reasoning engine is currently not part of any commercial RDBMS implementation. We show how a practical semantic query optimizer may be built utilising readily available semantic information, much of it already captured by meta-data typically stored in commercial RDBMS. We develop cost models which predict an upper bound to the amount of optimization one can expect when queries are pre-processed by a semantic optimizer. We present a series of empirical results to confirm the effectiveness or otherwise of various types of SQO and demonstrate the circumstances under which SQO can be effective.