Pub Date : 1998-02-23DOI: 10.1109/ICDE.1998.655774
J. Bedell
The core challenges associated with enterprise OLAP are how to structure the database and how to build a decision support architecture that allows for complex analysis and qualification. The primary components of an OLAP system-the database and the analysis engine-must be capable of handling large amounts of data in varying structures. Warehouses will continue to grow and contain data that is difficult if not impossible to store in fixed structures such as a star schema. In parallel, analysis requirements will continue to increase in complexity in terms of calculation, and qualification. OLAP tools must remove data size limitations and data structure requirements while providing a means of delivering advanced analytical functionality even for large data volumes. The key to overcoming these challenges lies in achieving tighter integration between analysis tools and databases. The database and the analytical engine must not impose restrictions on each other such that the ability to manage or analyze information in the warehouse is compromised.
{"title":"Outstanding challenges in OLAP","authors":"J. Bedell","doi":"10.1109/ICDE.1998.655774","DOIUrl":"https://doi.org/10.1109/ICDE.1998.655774","url":null,"abstract":"The core challenges associated with enterprise OLAP are how to structure the database and how to build a decision support architecture that allows for complex analysis and qualification. The primary components of an OLAP system-the database and the analysis engine-must be capable of handling large amounts of data in varying structures. Warehouses will continue to grow and contain data that is difficult if not impossible to store in fixed structures such as a star schema. In parallel, analysis requirements will continue to increase in complexity in terms of calculation, and qualification. OLAP tools must remove data size limitations and data structure requirements while providing a means of delivering advanced analytical functionality even for large data volumes. The key to overcoming these challenges lies in achieving tighter integration between analysis tools and databases. The database and the analytical engine must not impose restrictions on each other such that the ability to manage or analyze information in the warehouse is compromised.","PeriodicalId":264926,"journal":{"name":"Proceedings 14th International Conference on Data Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127378274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-02-23DOI: 10.1109/ICDE.1998.655808
S. Hibino, Elke A. Rundensteiner
We have developed a MultiMedia Visual Information Seeking (MMVIS) Environment designed to support an integrated approach to direct manipulation temporal querying and browsing of temporal relationship results. We address the optimization of queries specified via our visual query interface. Queries in MMVIS are incrementally specified and continuously refined multidimensional range queries. We present our k-Array index structure and its bucket based counterpart, the k-Bucket, as new indexes optimized for processing these direct manipulation queries. In an experimental evaluation comparing our k-Array and k-Bucket solutions to alternate techniques from the literature, we show that the k-Bucket performs generally equal to or better than the other techniques and is the best overall approach for such environments.
{"title":"Processing incremental multidimensional range queries in a direct manipulation visual query environment","authors":"S. Hibino, Elke A. Rundensteiner","doi":"10.1109/ICDE.1998.655808","DOIUrl":"https://doi.org/10.1109/ICDE.1998.655808","url":null,"abstract":"We have developed a MultiMedia Visual Information Seeking (MMVIS) Environment designed to support an integrated approach to direct manipulation temporal querying and browsing of temporal relationship results. We address the optimization of queries specified via our visual query interface. Queries in MMVIS are incrementally specified and continuously refined multidimensional range queries. We present our k-Array index structure and its bucket based counterpart, the k-Bucket, as new indexes optimized for processing these direct manipulation queries. In an experimental evaluation comparing our k-Array and k-Bucket solutions to alternate techniques from the literature, we show that the k-Bucket performs generally equal to or better than the other techniques and is the best overall approach for such environments.","PeriodicalId":264926,"journal":{"name":"Proceedings 14th International Conference on Data Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133979414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-02-23DOI: 10.1109/ICDE.1998.655772
Scott T. Leutenegger, M. Lopez
Past R tree studies have focused on the number of nodes visited as a metric of query performance. Since database systems usually include a buffering mechanism, we propose that the number of disk accesses is a more realistic measure of performance. We develop a buffer model to analyze the number of disk accesses required for spatial queries using R trees. The model can be used to evaluate the quality of R tree update operations, such as various node splitting and tree restructuring policies, as measured by query performance on the resulting tree. We use our model to study the performance of three well known R tree packing algorithms. We show that ignoring buffer behavior and using number of nodes accessed as a performance metric can lead to incorrect conclusions, not only quantitatively, but also qualitatively. In addition, we consider the problem of how many levels of the R tree should be pinned in the buffer.
{"title":"The effect of buffering on the performance of R-trees","authors":"Scott T. Leutenegger, M. Lopez","doi":"10.1109/ICDE.1998.655772","DOIUrl":"https://doi.org/10.1109/ICDE.1998.655772","url":null,"abstract":"Past R tree studies have focused on the number of nodes visited as a metric of query performance. Since database systems usually include a buffering mechanism, we propose that the number of disk accesses is a more realistic measure of performance. We develop a buffer model to analyze the number of disk accesses required for spatial queries using R trees. The model can be used to evaluate the quality of R tree update operations, such as various node splitting and tree restructuring policies, as measured by query performance on the resulting tree. We use our model to study the performance of three well known R tree packing algorithms. We show that ignoring buffer behavior and using number of nodes accessed as a performance metric can lead to incorrect conclusions, not only quantitatively, but also qualitatively. In addition, we consider the problem of how many levels of the R tree should be pinned in the buffer.","PeriodicalId":264926,"journal":{"name":"Proceedings 14th International Conference on Data Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131334124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-02-23DOI: 10.1109/ICDE.1998.655787
King-Lup Liu, A. Sistla, Clement T. Yu, N. Rishe
A.P. Sistla et al. (1997) designed a similarity-based video retrieval system. Queries were specified in a language called the Hierarchical Temporal Language (HTL). In this paper, we present several extensions of HTL. These extensions include queries that can have the negation operator and any other logical and temporal operators such as disjunction. Efficient algorithms for processing queries in the extended language are also presented.
{"title":"Query processing in a video retrieval system","authors":"King-Lup Liu, A. Sistla, Clement T. Yu, N. Rishe","doi":"10.1109/ICDE.1998.655787","DOIUrl":"https://doi.org/10.1109/ICDE.1998.655787","url":null,"abstract":"A.P. Sistla et al. (1997) designed a similarity-based video retrieval system. Queries were specified in a language called the Hierarchical Temporal Language (HTL). In this paper, we present several extensions of HTL. These extensions include queries that can have the negation operator and any other logical and temporal operators such as disjunction. Efficient algorithms for processing queries in the extended language are also presented.","PeriodicalId":264926,"journal":{"name":"Proceedings 14th International Conference on Data Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115149688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-02-23DOI: 10.1109/ICDE.1998.655768
Jarek Gryz
Query folding is a technique for determining how a query may be answered using a given set of resources, which may include materialized views, cached results of previous queries or queries answerable by other databases. The power of query folding can be considerably enhanced by taking into account integrity constraints that are known to hold on base relations. This paper describes an extension of query folding that utilizes inclusion dependencies to find foldings of queries that would otherwise be overlooked. We describe a complete strategy for finding foldings in the presence of inclusion dependencies and present a basic algorithm that implements that strategy. We also describe extensions to this algorithm when both inclusion and functional dependencies are considered.
{"title":"Query folding with inclusion dependencies","authors":"Jarek Gryz","doi":"10.1109/ICDE.1998.655768","DOIUrl":"https://doi.org/10.1109/ICDE.1998.655768","url":null,"abstract":"Query folding is a technique for determining how a query may be answered using a given set of resources, which may include materialized views, cached results of previous queries or queries answerable by other databases. The power of query folding can be considerably enhanced by taking into account integrity constraints that are known to hold on base relations. This paper describes an extension of query folding that utilizes inclusion dependencies to find foldings of queries that would otherwise be overlooked. We describe a complete strategy for finding foldings in the presence of inclusion dependencies and present a basic algorithm that implements that strategy. We also describe extensions to this algorithm when both inclusion and functional dependencies are considered.","PeriodicalId":264926,"journal":{"name":"Proceedings 14th International Conference on Data Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120892026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-02-23DOI: 10.1109/ICDE.1998.655810
Y. Theodoridis, E. Stefanakis, T. Sellis
The join query is one of the fundamental operations in database management systems (DBMSs). Modern DBMSs should be able to support non traditional data, including spatial objects, in an efficient manner. Towards this goal, spatial data structures can be adopted in order to support the execution of join queries on sets of multidimensional data. The paper introduces analytical models that estimate the cost (in terms of node or disk accesses) of join queries involving two multidimensional indexed data sets using R tree based structures. In addition, experimental results are presented, which show the accuracy of the analytical estimations when compared to actual runs on both synthetic and real data sets. It turns out that the relative error rarely exceeds 15% for all combinations, a fact that makes the proposed cost models useful tools for efficient spatial query optimization.
{"title":"Cost models for join queries in spatial databases","authors":"Y. Theodoridis, E. Stefanakis, T. Sellis","doi":"10.1109/ICDE.1998.655810","DOIUrl":"https://doi.org/10.1109/ICDE.1998.655810","url":null,"abstract":"The join query is one of the fundamental operations in database management systems (DBMSs). Modern DBMSs should be able to support non traditional data, including spatial objects, in an efficient manner. Towards this goal, spatial data structures can be adopted in order to support the execution of join queries on sets of multidimensional data. The paper introduces analytical models that estimate the cost (in terms of node or disk accesses) of join queries involving two multidimensional indexed data sets using R tree based structures. In addition, experimental results are presented, which show the accuracy of the analytical estimations when compared to actual runs on both synthetic and real data sets. It turns out that the relative error rarely exceeds 15% for all combinations, a fact that makes the proposed cost models useful tools for efficient spatial query optimization.","PeriodicalId":264926,"journal":{"name":"Proceedings 14th International Conference on Data Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120907618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-02-23DOI: 10.1109/ICDE.1998.655804
Banu Özden, S. Ramaswamy, A. Silberschatz
We study the problem of discovering association rules that display regular cyclic variation over time. For example, if we compute association rules over monthly sales data, we may observe seasonal variation where certain rules are true at approximately the same month each year. Similarly, association rules can also display regular hourly, daily, weekly, etc., variation that is cyclical in nature. We demonstrate that existing methods cannot be naively extended to solve this problem of cyclic association rules. We then present two new algorithms for discovering such rules. The first one, which we call the sequential algorithm, treats association rules and cycles more or less independently. By studying the interaction between association rules and time, we devise a new technique called cycle pruning, which reduces the amount of time needed to find cyclic association rules. The second algorithm, which we call the interleaved algorithm, uses cycle pruning and other optimization techniques for discovering cyclic association rules. We demonstrate the effectiveness of the interleaved algorithm through a series of experiments. These experiments show that the interleaved algorithm can yield significant performance benefits when compared to the sequential algorithm. Performance improvements range from 5% to several hundred percent.
{"title":"Cyclic association rules","authors":"Banu Özden, S. Ramaswamy, A. Silberschatz","doi":"10.1109/ICDE.1998.655804","DOIUrl":"https://doi.org/10.1109/ICDE.1998.655804","url":null,"abstract":"We study the problem of discovering association rules that display regular cyclic variation over time. For example, if we compute association rules over monthly sales data, we may observe seasonal variation where certain rules are true at approximately the same month each year. Similarly, association rules can also display regular hourly, daily, weekly, etc., variation that is cyclical in nature. We demonstrate that existing methods cannot be naively extended to solve this problem of cyclic association rules. We then present two new algorithms for discovering such rules. The first one, which we call the sequential algorithm, treats association rules and cycles more or less independently. By studying the interaction between association rules and time, we devise a new technique called cycle pruning, which reduces the amount of time needed to find cyclic association rules. The second algorithm, which we call the interleaved algorithm, uses cycle pruning and other optimization techniques for discovering cyclic association rules. We demonstrate the effectiveness of the interleaved algorithm through a series of experiments. These experiments show that the interleaved algorithm can yield significant performance benefits when compared to the sequential algorithm. Performance improvements range from 5% to several hundred percent.","PeriodicalId":264926,"journal":{"name":"Proceedings 14th International Conference on Data Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123397472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-02-23DOI: 10.1109/ICDE.1998.655792
Jürgen Sellentin, B. Mitschang
Intra/Internet technology has become a key issue in the development of modern systems. Nowadays, it is no longer sufficient to present static information sheets through the World Wide Web (WWW). Instead, we need interactive applications that may even compute complex results or process large data sets. In this paper, we describe a prototype based on Java and CORBA. Both represent modern concepts that have been developed to fulfill these requirements. Their combination results into the kind of data processing we want to apply to the WWW: (1) portable, powerful, structured and even reusable client programs instead of cryptic HTML scripts; (2) well-defined interfaces, and (3) efficient server processes separated from the WWW server and its CGI extensions. Communication is controlled by a fault-tolerant CORBA layer, which also enables server development using a different language than Java. Besides a discussion of CORBA and its data shipping capabilities, we take a closer look at Java and its runtime behavior, and we report on the experiences gathered with our prototype system and its testbed application. This system has also been used to gather experiences with and to influence the new language binding of the Standard Data Access Interface (SDAI) of the Standard for the Exchange of Product Data (STEP, ISO 10303) to Java.
intranet /Internet技术已成为现代系统开发中的一个关键问题。如今，仅仅通过万维网(WWW)提供静态信息表已经不够了。相反，我们需要能够计算复杂结果或处理大型数据集的交互式应用程序。本文描述了一个基于Java和CORBA的原型。两者都代表了为满足这些要求而开发的现代概念。它们的结合形成了我们想要应用于WWW的数据处理方式:(1)可移植的、强大的、结构化的、甚至可重用的客户端程序，而不是神秘的HTML脚本;(2)定义良好的接口，(3)与WWW服务器及其CGI扩展分离的高效服务器进程。通信由容错CORBA层控制，它还支持使用与Java不同的语言进行服务器开发。除了讨论CORBA及其数据传输功能之外，我们还深入研究了Java及其运行时行为，并报告了从原型系统及其测试平台应用程序中收集到的经验。该系统还被用于收集经验，并影响产品数据交换标准(STEP, ISO 10303)的标准数据访问接口(SDAI)与Java的新语言绑定。
{"title":"Data-intensive intra- and Internet applications-experiences using Java and CORBA in the World Wide Web","authors":"Jürgen Sellentin, B. Mitschang","doi":"10.1109/ICDE.1998.655792","DOIUrl":"https://doi.org/10.1109/ICDE.1998.655792","url":null,"abstract":"Intra/Internet technology has become a key issue in the development of modern systems. Nowadays, it is no longer sufficient to present static information sheets through the World Wide Web (WWW). Instead, we need interactive applications that may even compute complex results or process large data sets. In this paper, we describe a prototype based on Java and CORBA. Both represent modern concepts that have been developed to fulfill these requirements. Their combination results into the kind of data processing we want to apply to the WWW: (1) portable, powerful, structured and even reusable client programs instead of cryptic HTML scripts; (2) well-defined interfaces, and (3) efficient server processes separated from the WWW server and its CGI extensions. Communication is controlled by a fault-tolerant CORBA layer, which also enables server development using a different language than Java. Besides a discussion of CORBA and its data shipping capabilities, we take a closer look at Java and its runtime behavior, and we report on the experiences gathered with our prototype system and its testbed application. This system has also been used to gather experiences with and to influence the new language binding of the Standard Data Access Interface (SDAI) of the Standard for the Exchange of Product Data (STEP, ISO 10303) to Java.","PeriodicalId":264926,"journal":{"name":"Proceedings 14th International Conference on Data Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128720865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-02-23DOI: 10.1109/ICDE.1998.655786
Eenjun Hwang, V. S. Subrahmanian, B. Prabhakaran
Considers a distributed video server environment where video movies need not be stored entirely in one server. Blocks of a video movie are be distributed and replicated over multiple video servers. Customers are served by one video server. This video server, termed the originating server, might have to interact with other servers for downloading missing blocks of the requested movie. We present three types of presentation plans that an originating server can possibly construct for satisfying a customer's request. A presentation plan can be considered as a detailed (temporally synchronized) sequence of steps carried out by the originating server for presenting the requested movie to the customer. The creation of presentation plans involves obtaining commitments from other video servers and the network service provider, as well as making local resource commitments, within the limitations of available bandwidth, available buffer and customer consumption rates. For evaluating the goodness of a presentation plan, we introduce two measures of optimality for presentation plans: minimizing the waiting time for a customer and minimizing the access bandwidth. We present algorithms for computing optimal presentation plans and compare their performance experimentally. We have also mathematically proved certain results for the presentation plans.
{"title":"Distributed video presentations","authors":"Eenjun Hwang, V. S. Subrahmanian, B. Prabhakaran","doi":"10.1109/ICDE.1998.655786","DOIUrl":"https://doi.org/10.1109/ICDE.1998.655786","url":null,"abstract":"Considers a distributed video server environment where video movies need not be stored entirely in one server. Blocks of a video movie are be distributed and replicated over multiple video servers. Customers are served by one video server. This video server, termed the originating server, might have to interact with other servers for downloading missing blocks of the requested movie. We present three types of presentation plans that an originating server can possibly construct for satisfying a customer's request. A presentation plan can be considered as a detailed (temporally synchronized) sequence of steps carried out by the originating server for presenting the requested movie to the customer. The creation of presentation plans involves obtaining commitments from other video servers and the network service provider, as well as making local resource commitments, within the limitations of available bandwidth, available buffer and customer consumption rates. For evaluating the goodness of a presentation plan, we introduce two measures of optimality for presentation plans: minimizing the waiting time for a customer and minimizing the access bandwidth. We present algorithms for computing optimal presentation plans and compare their performance experimentally. We have also mathematically proved certain results for the presentation plans.","PeriodicalId":264926,"journal":{"name":"Proceedings 14th International Conference on Data Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117352691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-02-23DOI: 10.1109/ICDE.1998.655812
Ashok Savasere, E. Omiecinski, S. Navathe
Mining for association rules is considered an important data mining problem. Many different variations of this problem have been described in the literature. We introduce the problem of mining for negative associations. A naive approach to finding negative associations leads to a very large number of rules with low interest measures. We address this problem by combining previously discovered positive associations with domain knowledge to constrain the search space such that fewer but more interesting negative rules are mined. We describe an algorithm that efficiently finds all such negative associations and present the experimental results.
{"title":"Mining for strong negative associations in a large database of customer transactions","authors":"Ashok Savasere, E. Omiecinski, S. Navathe","doi":"10.1109/ICDE.1998.655812","DOIUrl":"https://doi.org/10.1109/ICDE.1998.655812","url":null,"abstract":"Mining for association rules is considered an important data mining problem. Many different variations of this problem have been described in the literature. We introduce the problem of mining for negative associations. A naive approach to finding negative associations leads to a very large number of rules with low interest measures. We address this problem by combining previously discovered positive associations with domain knowledge to constrain the search space such that fewer but more interesting negative rules are mined. We describe an algorithm that efficiently finds all such negative associations and present the experimental results.","PeriodicalId":264926,"journal":{"name":"Proceedings 14th International Conference on Data Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130895097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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