This paper discusses and analyses teaching reforms on fundamental courses of computer science in colleges and universities.It illustrates its points by using Data Structure course as an example and the aim of this paper is to set up a demonstration for teaching reforms in other fundamental courses of computer science or in other majors.
XML documents compression is a focus problem in XML data management.We give the novel algorithm of mining a frequent XML tag sequence.In the meantime,An XML clustering algorithm is proposed using the mined frequent tag sequence.Finally,an XML document storage strategy is put forward.
In computer system,the access control security is a most important problem.This paper presented an agency strategy of access control rights management owing to logical access control management,which authorizes the users management to grant or forbid other users access rights.Also,it gave a set of rules to achieve the accuracy agents,conflict resolution and the hierarchy of the authorization delivery strategy along the main body and access to the object.
There are many tasks such as evaluating,adjusting,or modifying the database system to maintain it.To keep the database system running normally,database administrator(DBA) must do some daily maintenance work,which includes daily database cleanup,maintaining and rebuilding index,regularly backup the database,and maintaining and backup the log files etc.Taking the PostgreSQL database management system as an example,this paper presents a comprehensive analysis of the daily maintenance work for a database system.
Access control is needed in any system where the resources are shared by different users.In this paper,we develop a logic based approach for decentralized authorization management in which users are delegated,granted or for- bidden some access rights.A set of general logic rules are provided to handle the delegation correctness,conflict reso- lution and authorization propagation along the hierarchies of subjects,objects and access rights.By combining these general rules with application-specific rules defined by users,we can derive the authorizations holding in the system.In addition,some semantic properties are further investigated.
The object relational database system PostgreSQL provides the following index types: B-tree,R-tree,GiST,and Hash.Different index types provide the most optimised methods for different query types.Most of them are suitable to many situations,especially to equal query and range query on ordered data.This paper investigates and analyses the index mechanism in PostgreSQL system based on the most common B-tree index.
The object relational database is a new database management system,which has the properties of both the relational database system and the object-oriented database system.It can be used to store and manage not only objects and rules but also relational data.In order to support the object relational database management system to run for long time,database vacuum is very necessary.PostgreSQL is an open source object relational database management system.Its statistics collector which is an important component of the database vacuum mechanism is analyzed,and the kinds of statistics information it can collect,main functions,data structures,and implementation algorithms are griven,which are helpful for maintaining and improving the database system.
This paper describes a method of modeling Web servers and managing unpredictable server load using H-infinity robust control theory.It shows that a Web server may be simulated as a multi-tank system.A robust Web server model is subject to unknown additive load disturbances and uncertain model matching.Overload control techniques are based on adaptive admission control to achieve timing guarantees.The paper evaluates the performance of the model by using a complex simulation that is subject to varying model parameters and massive overload.
This paper describes a method of modeling Web servers and managing unpredictable server load using H-infinity robust control theory.It shows that a Web server may be simulated as a multi-tank system.A robust Web server model is subject to unknown additive load disturbances and uncertain model matching.Overload control techniques are based on adaptive admission control to achieve timing guarantees.The paper evaluates the performance of the model by using a complex simulation that is subject to varying model parameters and massive overload.
With the increasing importance and pervasiveness of Internet services, distributed database system on the Internet are becoming more and more widespread. Since the appearance of distributed database system, data collection, store and procession have transformed from concen- tration into distribution, from close into open. Analyses the development trend and working principle of the distributed database system, and analyses the corresponding technology of the distributed dat- abase system, proposes the technological application principle when use the distributed database sys- tem.
This article mainly discusses some basic factors to improve the quality of computer theory education as follows:education aim,education aspects,teachers,students as well as education enviroment.
A big and flexible DBMS(DataBase Manager System) should not only support a variety of data objects, but also have some features such as sharablity,flexibility,expandability and safety. In order to make the system run efficiently and smoothly, there’s an unignorable mechanism in DBMS, the Data Base Vacuum mechanism. This thesis mainly emphasizes on an important part of the Vacuum in RDBMS(Relative DataBase Manager System): state data's statistic collector mechanism. It will be meaningful for the study of database maintenance technology.
School is the base for knowledge creativity, transmission and application, and the cradle for feeding creative people. The quality of education directly influences the quality of people. The quality of the education is of vital importance in a school. This article mainly discusses some basic factorsto improve the quality of thoery education as follows: education aim, education aspects, teachers, students as well as education enviroment. From theory to practice, this article makes a primary discussion, on how to improve the quality of theory education.
