Recent studies have addressed that the cache be havior is important in the design of main memory index structures. Cache-conscious indices such as the CSB^＋-tree are shown to outperform conventional main memory indic...Recent studies have addressed that the cache be havior is important in the design of main memory index structures. Cache-conscious indices such as the CSB^＋-tree are shown to outperform conventional main memory indices such as the AVL-tree and the T-tree. This paper proposes a cacheconscious version of the T-tree, CST-tree, defined according to the cache-conscious definition. To separate the keys within a node into two parts, the CST-tree can gain higher cache hit ratio.展开更多
In this paper, we propose a new method based on index to realize IR-style Chinese keyword search with ranking strategies in relational databases. This method creates an index by using the related information of tuple ...In this paper, we propose a new method based on index to realize IR-style Chinese keyword search with ranking strategies in relational databases. This method creates an index by using the related information of tuple words and presents a ranking strategy in terms of the nature of Chinese words. For a Chinese keyword query, the index is used to match query search words and the tuple words in index quickly, and to compute similarities between the query and tuples by the ranking strategy, and then the set of identifiers of candidate tuples is generated. Thus, we retrieve top-N results of the query using SQL selection statements and output the ranked answers according to the similarities. The experimental results show that our method is efficient and effective.展开更多
There are several indexing techniques that can optimize system performances. The choice of the right index type in a schema can improve the DB performances by up to 80%. Unfortunately the illustrations of the various ...There are several indexing techniques that can optimize system performances. The choice of the right index type in a schema can improve the DB performances by up to 80%. Unfortunately the illustrations of the various techniques are scattered over a number of texts and manuals, and the courses for database designers are often somewhat incomplete. The present paper shows a didactical experience which tackles this kind of limitations. In particular, the authors have prepared a textbook that includes twenty-one different index formats; it discusses advantages and disadvantages of each indexing technique, and has been positively validated during advanced courses on relational database design.展开更多
An outsource database is a database service provided by cloud computing companies.Using the outsource database can reduce the hardware and software＇s cost and also get more efficient and reliable data processing capa...An outsource database is a database service provided by cloud computing companies.Using the outsource database can reduce the hardware and software＇s cost and also get more efficient and reliable data processing capacity.However,the outsource database still has some challenges.If the service provider does not have sufficient confidence,there is the possibility of data leakage.The data may has user＇s privacy,so data leakage may cause data privacy leak.Based on this factor,to protect the privacy of data in the outsource database becomes very important.In the past,scholars have proposed k-anonymity to protect data privacy in the database.It lets data become anonymous to avoid data privacy leak.But k-anonymity has some problems,it is irreversible,and easier to be attacked by homogeneity attack and background knowledge attack.Later on,scholars have proposed some studies to solve homogeneity attack and background knowledge attack.But their studies still cannot recover back to the original data.In this paper,we propose a data anonymity method.It can be reversible and also prevent those two attacks.Our study is based on the proposed r-transform.It can be used on the numeric type of attributes in the outsource database.In the experiment,we discussed the time required to anonymize and recover data.Furthermore,we investigated the defense against homogeneous attack and background knowledge attack.At the end,we summarized the proposed method and future researches.展开更多
Interpretation results of RS images were taken as the foundation, ETM RS images of July 15, 2009 as the data source, ENVI was applied for the preprocessing, Arc GIS used to finish the interpretation, master data obtai...Interpretation results of RS images were taken as the foundation, ETM RS images of July 15, 2009 as the data source, ENVI was applied for the preprocessing, Arc GIS used to finish the interpretation, master data obtained, and VB used to complete program development. 12 representative landscape pattern indexes were selected, Excel data used to create Access database, and VB used to complete the program development. Selection of landscape pattern indexes, program development process and program usage were summarized, through comparing its results with Excel calculation results, it was found that calculation results of this program were correct, the usage was convenient, so needs of most users could be satisfied.展开更多
基金Supported bythe National High Technology of 863Project (2002AA1Z2308 ,2002AA118030)
文摘Recent studies have addressed that the cache be havior is important in the design of main memory index structures. Cache-conscious indices such as the CSB^＋-tree are shown to outperform conventional main memory indices such as the AVL-tree and the T-tree. This paper proposes a cacheconscious version of the T-tree, CST-tree, defined according to the cache-conscious definition. To separate the keys within a node into two parts, the CST-tree can gain higher cache hit ratio.
文摘In this paper, we propose a new method based on index to realize IR-style Chinese keyword search with ranking strategies in relational databases. This method creates an index by using the related information of tuple words and presents a ranking strategy in terms of the nature of Chinese words. For a Chinese keyword query, the index is used to match query search words and the tuple words in index quickly, and to compute similarities between the query and tuples by the ranking strategy, and then the set of identifiers of candidate tuples is generated. Thus, we retrieve top-N results of the query using SQL selection statements and output the ranked answers according to the similarities. The experimental results show that our method is efficient and effective.
文摘There are several indexing techniques that can optimize system performances. The choice of the right index type in a schema can improve the DB performances by up to 80%. Unfortunately the illustrations of the various techniques are scattered over a number of texts and manuals, and the courses for database designers are often somewhat incomplete. The present paper shows a didactical experience which tackles this kind of limitations. In particular, the authors have prepared a textbook that includes twenty-one different index formats; it discusses advantages and disadvantages of each indexing technique, and has been positively validated during advanced courses on relational database design.
文摘An outsource database is a database service provided by cloud computing companies.Using the outsource database can reduce the hardware and software＇s cost and also get more efficient and reliable data processing capacity.However,the outsource database still has some challenges.If the service provider does not have sufficient confidence,there is the possibility of data leakage.The data may has user＇s privacy,so data leakage may cause data privacy leak.Based on this factor,to protect the privacy of data in the outsource database becomes very important.In the past,scholars have proposed k-anonymity to protect data privacy in the database.It lets data become anonymous to avoid data privacy leak.But k-anonymity has some problems,it is irreversible,and easier to be attacked by homogeneity attack and background knowledge attack.Later on,scholars have proposed some studies to solve homogeneity attack and background knowledge attack.But their studies still cannot recover back to the original data.In this paper,we propose a data anonymity method.It can be reversible and also prevent those two attacks.Our study is based on the proposed r-transform.It can be used on the numeric type of attributes in the outsource database.In the experiment,we discussed the time required to anonymize and recover data.Furthermore,we investigated the defense against homogeneous attack and background knowledge attack.At the end,we summarized the proposed method and future researches.
基金Supported by Social Development Program of Lianyungang Bureau of Science and Technology,Jiangsu Province:RS-based Research on the Eco-environment Evolution of Coastal Regions in Lianyungang(SH0811)~~
文摘Interpretation results of RS images were taken as the foundation, ETM RS images of July 15, 2009 as the data source, ENVI was applied for the preprocessing, Arc GIS used to finish the interpretation, master data obtained, and VB used to complete program development. 12 representative landscape pattern indexes were selected, Excel data used to create Access database, and VB used to complete the program development. Selection of landscape pattern indexes, program development process and program usage were summarized, through comparing its results with Excel calculation results, it was found that calculation results of this program were correct, the usage was convenient, so needs of most users could be satisfied.
