Research on Materialized View Selection

定义了数据仓库领域的视图选择问题,并讨论了与该问题相关的代价模型、收益函数、代价计算、约束条件和视图索引等内容;介绍了3大类视图选择方法,即静态方法、动态方法和混合方法,以及各类方法的代表性研究成果;最后展望未来的研究方向.Definition of view selection issue in the field of data warehouses is presented, followed by the discussion of related problems, such as cost model, benefit function, cost computation, restriction condition, view index, etc. Then three categories of view selection methods, namely, static, dynamic and hybrid methods are discussed. For each method, some representative work is introduced. Finally some future trends in this area are discussed.Supported by the National Natural Science Foundation of China under Grant No.60473051 (国家自然科学基金); the National High-Tech Research and Development Plan of China under Grant Nos.2007AA01Z191, 2006AA01Z230 (国家高技术研究发展计划(863)

Change Data Capture in Real-Time Active Data Warehouses: A Survey

本文是在北京大学数据库实验室攻读博士学位期间发表的。实时主动数据仓库是数据仓库的最新发展阶段和未来发展趋势,它为企业提供了对战略决策和战术决策的双重支持.实时主动数据仓库中包含两类数据,即实时数据和非实时数据,相应地,需要两种不同类型的变化数据捕捉方法,即支持实时变化数据捕捉的方法和普通的(不支持实时的)变化数据捕捉方法.结合在该领域的研究经验,对实时主动数据仓库中可以使用的多种变化数据捕捉方法进行了系统地论述,并比较各种方法的应用条件、优点、缺点和适用场合。Real-time active data warehouse is the most recent stage in the evolution history of data warehouses．It supports both strategic decision and tactic decision，which will bring great benefits to organizations．There are two types of data existing in real-time active data warehouses，i．e．，real-time data and non-real-time data．Accordingly，change data capture methods are classified into tWO kinds，including those supporting real-time change data capture and those not supporting real-time change data capture．Based on extensive research work in this field，those change data capture methods are systematically discussed，which may meet the requirements in real-time active data warehouses．国家自然科学基金项目(60473015)；国家“863”高技术研究发展计划基金项目(2006AAl2Z217)；HP中国实验室联合项

Research on Requirement-based Real-time Data Integration in Real-time Active Data Warehouses

本文是在北京大学数据库实验室攻读博士学位期间发表的。实时数据集成是实时主动数据仓库研究领域的一个重要问题。现有的研究成果都是从技术角度出发，而并没有考虑具体的商务应用需求。而在大型商务应用中，即使采用过滤规则只捕捉感兴趣的变化数据，也会产生大量的数据集成工作，从而导致不必要的沉重系统开销，同时还很有可能出现系统响应缓慢和用户需求无法得到满足等情况。本文从应用角度出发，提出了实时主动数据仓库中面向需求的实时数据集成方法，包括被频繁请求的数据的实时集成、满足突发请求的实时数据集成和由用户决定的实时数据集成。针对不同的商务需求，采用不同的数据集成策略，可以很好地满足不同类型的应用需求。Real-time data integration is a very important aspect in the field of real-time active data warehouse. Almost all the available research work now is from a technological point of view instead of an application angle. While in the real-world business application, a large amount of real-time data integration needs to be done even with the help of change data capture technology to integrate only the interesting part of the data from the data source, which will usually lead to the deteriorated system performance and fail to satisfy the business requirement in some cases. From an application angle, we here propose three requirement-based real-time data integration methods, including: real-time integration for the frequently requested data, real-time integration for the suddenly arising requirement and user-decided real-time integration. By adopting the appropriate method for the specific application occasion, we can better satisfy the various business requirements.国家自然科学基金项目(60473015)；国家“863”高技术研究发展计划基金项目(2006AAl2Z217)；HP中国实验室联合项

Materialized Views Selection of Multi-Dimensional Data in Real-Time Active Data Warehouses

通过基于主动决策引擎日志的数据挖掘来找到分析规则的CUBE 使用模式,从而为多维数据实视图选择算法提供重要依据;在此基础上设计了3A 概率模型,并给出考虑CUBE 受访概率分布的视图选择贪婪算法PGreedy(probability greedy), 以及结合视图挽留原则的视图动态调整算法. 实验结果表明, 在实时主动数据仓库环境下,PGreedy 算法比BPUS(benefit per unit space)算法具有更好的性能. In this paper, data mining based on the log of active decision engine is introduced to find the CUBE using pattern of analysis rules, which can be used as important reference information for materialized views selection. Based on it, a 3A probability model is designed, and the greedy algorithm, called PGreedy (probability greedy), is proposed, which takes into account the probability distribution of CUBE. Also view keeping rule is adopted to achieve better performance for dynamic view adjusting. Experimental results show that PGreedy algorithm can achieve better performance than BPUS (benefit per unit space) algorithm in real-time active data warehouses environment.Supported by the National Natural Science Foundation of China under Grant No.60473051 (国家自然科学基金); the China HP Co. and Peking University Joint Project (北京大学-惠普(中国)合作项目

Dealing with Query Contention Issue in Real-time Data Warehouses by Dynamic Multi-level Caches

The issue of query contention and scalability is the most difcult issue facing organizations deploying real-time data warehouse s olutions. The contention between complex se-lects and continuous inserts tends to severely limit the scal-ability of the data warehouses. I n this paper, we present a new method called dynamic multi-level caches, to effec-tively deal with the problem of query contention and scal-ability in real-time data warehouses. We differentiate be-tween queries with various data freshness requirements, and use multi-level caches to satisfy these different require-ments. Every query arriving at the system will be automat-ically redirected to the corresponding cache to access the required data, which means that the query loads are dis-tributed to multi-level caches instead of becoming blocked in the only one cache due to the contention between query and update operations. Extensive experiments on s everal real datasets s how that our method can effectively balance the query loads among multi-level caches and achieve desirable system performance

User-oriented Materialized View Selection

The problem of materialized view selection has been long researched, and many approaches have been proposed to deal with this issue. However, all the methods proposed to date strive toward improving the overall query performance, instead of being user-oriented. In this paper, we propose a new user-oriented method, called SOMES (uSerOriented Materialized viEw Selection), aiming at achieving better performance for view selection problem. SOMES takes into account query characteristics of different users, in which, users are classified into different groups according to their query characteristics, and various user groups are provided with their own windows, user view windows containing the views involved in their own query process. Experimental results show that our method can achieve desirable performance improvements over other methods such as BPUS and FPUS

Architecture of a Database System

数据库管理系统（DBMS）广泛存在于现代计算机系统中，并且是其重要的组成部分。它是学术界以及工业界数十年研究和发展的成果。在计算机发展史上，数据库属于最早开发的多用户服务系统之一，因此，它的研究也催生了许多为保证系统可拓展性以及稳定性的系统开发技术，这些技术如今被应用于许多其他的领域。虽然许多数据库的相关算法和概念广泛见于教科书中，但关于如何让一个数据库工作的系统设计问题却鲜有资料介绍。本文从体系架构角度探讨数据库设计的一些准则，包括处理模型、并行架构、存储系统设计、事务处理系统、查询处理及优化结构以及具有代表性的共享组件和应用。当业界有多种设计方式可供选择时，我们以当前成功的商业开源软件作为参考标准

Effect of Refractive Index of Substrate on Fabrication and Optical Properties of Hybrid Au-Ag Triangular Nanoparticle Arrays

以石英和不同型号的玻片为基底,系统研究了基底折射率对周期性金银复合纳米阵列的制备及其光学性能的影响。采用离散偶极子近似(ddA)数值方法研究了复合阵列的局部表面等离子共振(lSPr)光谱特性,计算结果表明,当基底折射率为1.43和1.68时,纳米阵列的折射率灵敏度(rIS)和品质因子(fOM)比较优异。利用纳米球刻蚀法(nSl)制备了二维周期性复合纳米点阵结构,实验结果表明,当基底折射率为1.43和1.68时,基底与贵金属纳米颗粒有较好的粘合度,纳米阵列结构形貌比较规则清晰。Based on the substrate of silica and different types of slides, the effect of refractive index of substrate on fabrication and optical properties of hybrid Au- Ag triangular periodic nanoparticle arrays is systematically investigated.The optical spectrum of localized surface plasmon resonance(LSPR) simulated by discrete dipole approximation(DDA) numerical method shows that the nanoparticle arrays can obtain better refractive index sensitivity(RIS) and figure of merit(FOM), when refractive index of substrate is 1.43 and 1.68, respectively.The nanosphere lithography(NSL) is used to fabricate the periodic nanostructure arrays.The experimental results demonstrate that when refractive index of substrate is 1.43 and 1.68, nanoparticles and substrate have better adhesive ability.Meanwhile, the nanoparticles both form a large-scale monolayer array with the hexagonally close-packed structure.国家自然科学基金(11074207); 厦门科技项目(3502Z20143020;2012S0484); 福建省教育厅科技项目(JA11157;12200); 集美大学潘金龙基金(C512038

黔西北土法炼锌区水土流失的特点及防治对策

作者简介: 吴桂容( 1970- ) , 女, 广西贺州人, 博士研究生, 副教授, 主要从事污染生态学研究。E - mail: hzwgr510@ 163. com。通信作者: 敖子强, 博士研究生, 主要从事环境生态和污染生态学研究。E - m ai:l aoz iq iang628@ 163. com。通过对土法炼锌区的土壤、废渣、植物、地表水和沉积物进行实地调查和采样分析,发现土法炼锌区水土流失主要是由于含有SO2和重金属的废气导致植被严重破坏、土壤裸露造成的;水土流失同时导致了重金属的迁移扩散,污染土壤中重金属可溶态比重大,而废渣中重金属可溶态比重小,主要随废渣一起流失。减少土法炼锌区水土流失的主要途径是恢复植被和利用工程措施将废渣固定。对于污染土壤来说限制因子是土壤pH值低,可溶态重金属比重大,主要对策是增加土壤的pH值,选择耐酸性和耐重金属的树种恢复植被;对于废渣来说限制因子是废渣持水保肥能力差,重金属含量高,及废渣本身的结构疏松,主要对策是保持废渣的pH值不降低,利用工程措施将废渣固定,及改变土壤的结构来恢复植被;废渣和污染土壤上的先锋植物醉鱼草(Buddleja lindleyana)可作为首选来恢复植被。贵州省科学技术基金(编号:20062014);广西重点实验室研究基金(编号:桂科能0704K002

Reclamation technology on preventing heavy metal pollution from landfill of indigenous zinc smelting areas

作者简介：敖子强（1975－），贵州德江人，男，博士生，主要从事环境生 态和污染生态学研究。福建厦门大学生命科学学院，361005。 Email: [email protected] 通信作者：严重玲（1959－），贵州贵阳人，男，教授，主要从事污染生 态学研究。福建厦门大学生命科学学院，361005。Email: [email protected][中文文摘]：黔西北赫章县炼锌造成大量的废弃地，土地复垦成为当地面临的主要问题。为大面积的土地复垦提供基础数据，在平整的废渣堆上用0、25 和50 kg/m2 的碱石灰做隔离层，然后在隔离层上覆以30、45 和60 cm 的非污染区土壤，共9个处理；选用当地的主要农作物红豆、白菜、玉米和马铃薯进行试验。通过近2 a 对红豆、白菜、玉米和马铃薯可食部 分和复垦土壤的重金属进行One-Way ANOVA （LSD）分析和富集系数比较得出碱石灰隔离层降低了农作物可食部分的重金属含量；玉米是对重金属富集系数最小的农作物，适合作为土地复垦的首选农作物，而白菜对重金属的富集系数最大，不适合在炼锌区复垦土壤种植；经济有效的碱石灰隔离层厚度为25 kg/m，复垦土壤的厚度为30 cm。[英文文摘]Due to indigenous zinc smelting, lots of lands were polluted and abandoned in Hezhang County, Guizhou Province. The reclamation of polluted soils is becoming more important to improve environmental protection and to prompt agricultural production in these areas. In the present study, total of nine treatments of different amount of lime (0, 25 and 50 kg/m2) was used as isolation layer in the flat slag heap, and then the isolation layer was covered with different amount of non-contamination soil (30, 45 and 60 cm), respectively. During the following two years, bean (Phaseolus angularis), Chinese cabbage (Brassica chinensis), maize (Zea mays) and potato (Solanum tuberosum) were planted,concentrations of some metals (Zn, Pb, Cd) in soils and the edible part of the crops were determined to assess the effects of reclamation by statistical analysis of One-Way ANOVA (LSD). The results indicated that metal concentrations in edible part of the crops were decreased by the treatments of limestone isolation layer; maize had the lowest enrichment factor of heavy metals among the four crops, while Chinese cabbage had the highest content, demonstrating that maize was more suitable to be cultivated compared with the others, lime as isolation layer could significantly reduce the accumulation of heavy metals in the edible part of the crops, and 25 kg/m2 lime isolation layer combined with 30 cm non-contamination soil cover showed the effective reclamation result.国家自然科学基金(30530150,40673064);福建省高校创新团队培育计划;贵州省科学技术基金(20062014