“数据库应用基础”开放式实验平台与实验过程综合自动评价系统研究

介绍如何利用开放式网络平台进行"数据库应用基础"课程实验教学改革,并对建立客观、科学、完整的学生实验结果评价体系和评价系统进行了探索。     

A remark on the complexity of consistent conjunctive query answering under primary key violations

A natural way for capturing uncertainty in the relational data model is by allowing relations that violate their primary key. A repair of such relation is obtained by selecting a maximal number of tuples without ever selecting two tuples that agree on their primary key. Given a Boolean query q, CERTAINTY(q) is the problem that takes as input a relational database and asks whether q evaluates to true on every repair of that database. In recent years, CERTAINTY(q) has been studied primarily for conjunctive queries. Conditions have been determined under which CERTAINTY(q) is coNP-complete, first-order expressible, or not first-order expressible. A remaining open question was whether there exist conjunctive queries q without self-join such that CERTAINTY(q) is in PTIME but not first-order expressible. We answer this question affirmatively.     

Efficient skycube computation using point and domain-based filtering

Skyline queries have been increasingly used in multi-criteria decision making and data mining applications. They retrieve a set of interesting points from a potentially large set of data points. A point is said to be interesting if it is not dominated by any other point. Skyline cube (skycube) consists of skylines of all possible non-empty subsets of a given set of dimensions. In this paper, we propose two algorithms for computing skycube using bitmaps that are derivable from indexes. The Point-based skycube algorithm is an improvement over the existing Bitmap algorithm, extended to compute skycube. The Point-based algorithm processes one point at a time to check for skylines in all subspaces. The Domain-based skycube algorithm views points as value combinations and probes entire search space for potential skyline points. It significantly reduces bitmap access for low cardinality dimensions. Our experimental study shows that the two algorithms strictly dominate, or at least comparable to, the current skycube algorithm in most of the cases, suggesting that such an approach could be a useful addition to the set of skyline query processing techniques.     

Efficient evaluation of query rewriting plan over materialized XML view

The query rewriting plan generation over XML views has received wide attention recently. However, little work has been done on efficient evaluation of the query rewriting plans, which is not trivial since the plan may contain an exponential size of sub-plans. This paper investigates the reason for the potentially exponential number of sub-plans, and then proposes a new space-efficient form called ABCPlan (Plan with Automata Based Combinations) to equivalently represent the original query rewriting plan. ABCPlan contains a set of buckets containing suffix paths in the query tree and an automata to indicate the combination of the suffix paths from different buckets as valid query rewriting sub-plans. We also design an evaluation method called ABCScan, which constructs a unified evaluation tree for the ABCPlan and handles the evaluation tree in one scan of the XML view. In the evaluation, we introduce node existence automata to encode the structure of the sub-tree and convert the satisfaction of the ABCPlan into the intersection problem of deterministic finite automata. The experiments show that ABCPlan based method outperforms existing methods significantly in terms of scalability and efficiency.     

中原探区地震勘探数据可视化共享系统研究与实现

随着油田勘探开发程度的不断提高,积累了大量的地震成果数据资料,为了有效地管理和应用这些资料,提高勘探开发研究工作效率,进行了地震成果数据可视化应用系统研发。应用现代信息技术,整合离散的地震成果数据资源,构建面向勘探开发研究人员的网络化、可视化的管理与共享服务体系,实现数据采集、加工、保存的标准化、规范化。分析了地震成果数据分类和管理关键问题,介绍了地震成果数据共享应用系统的技术思路、建设目标、系统安全策略和系统架构。最后阐述了在研发建设过程中所采用的几项关键技术和具体实现效果。     

Vertical partitioning for flash and HDD database systems

Recent advances in flash memory technology have greatly enhanced the capability of flash memory to address the I/O bottleneck problem. Flash memory has exceptional I/O performance compared to the hard disk drive (HDD). The superiority of flash memory is especially visible when dealing with random read patterns. Even though the cost of flash memory is higher than that of HDD storage, the popularity of flash memory is increasing at such a pace that it is becoming a common addition to the average computer. Recently, flash memory has been made into larger devices called solid state drives (SSDs). Although these devices can offer capacities comparable to HDDs, they are considerably more expensive per byte.Our research aims to increase the I/O performance of database systems by using a small amount of flash memory alongside HDD storage. The system uses a fully vertically partitioned storage structure where each column is stored separately on either the HDD or SSD. Our approach is to assign the columns into the SSD which will benefit the most from the characteristics of flash memory. We prove this problem is NP-complete and propose an optimal dynamic programming solution and a faster greedy heuristic solution.A system simulator has been implemented and experiments show that the overall I/O costs can be greatly reduced using only a limited amount of flash memory. The results show the greedy heuristic solution performed similarly to the more expensive dynamic programming solution for the situations tested.     

信息战中数据访问和集成模型设计与实现

提出了一种信息访问和集成模型的实现策略,即在不同种类的信息资源和信息应用之间构建1个中间层软降——“虚拟数据库系统”,通过“虚拟数据库系统”提供的标准访问接口及统一数据格式对信息战环境中各种分布的、异构的、不同种类的信息资源进行动态访问和集成,以此来提高信息的可访性、可用性、时效性、安全性。     

Visual Basic程序开发中数据库访问技术的探讨

Visual Basic是世界上使用人数最多的,微软公司开发的包含协助开发环境的事件驱动编程语言。它具有良好的图形用户界面（GUI）和强大的控件功能,并可以轻松地通过DAO、RDO、ADO等对数据库进行连接。该文主要对VB访问数据库的方案进行探讨．使用户从VB访问数据库的众多方法中,选择一种有利于开发人员与应用软件开发的方案,使用户能够更好了解VB的数据库编程功能．开发出的软件更具有现实的意义,而且适应该行业未来的发展。     

基于嵌入式的远程电源控制系统

随着以太网技术的发展,远程电源监控在各个领域应用越来越广泛。提出了以以太网作为远程终端和前端服务器通讯的介质,对远程嵌入式电源进行控制技术的研究。根据远程客户端采集信息,具体分析得出了对远程电源的控制要求,通过数据库作为接口,和服务器控制程序进行通信,服务器程序通过循环检测数据库的信息,更新控制信息的变化,利用TCP/IP协议,通过以太局域网发送控制信号,实现对远程终端嵌入式电源的控制。设计了具体的信息采集流程,得到与实际需求相符合的控制要求。     

基于倒排索引的密文数据库检索方法研究

针对实际密文数据库的应用,在全文检索倒排索引技术的基础上,设计了一种通过密文倒排索引文件对其进行快速检索的方法。密文索引文件中主要包含有索引项、相对应的记录主键等信息。检索时,通过用检索词匹配索引文件中的索引项,找到对应的记录主键集合,再根据记录主键集合查询密文数据库,获取相应的密文数据,进行解密即可获取明文数据信息。整个检索过程中不对数据库进行解密,从而实现了在不解密的情况下对密文数据库的快速检索。