We also discuss the classification of topk query processing techniques in relational databases with different design dimensions. Probabilistic topk dominating queries in uncertain databases. Some techniques produce exact answers, while others allow for approximate answers, or deal with uncertain data. Exact processing of uncertain topk queries in multi. In this paper, we introduce the top k query processing in relational database system. Skyline queries icde01,sigmod06 kregret queries vldb10,sigmod12,icde14 orderbased skyline queries sigmod10 let me state some interesting queries in the literature. In a type of considered uncertainty, each record is associated with an existence probability, i. However, in many cases, ta does not terminate even if the final topk results have been found for some time. Efficient processing of topk queries is a crucial requirement in many interactive environments that involve massive amounts of data. Third, the prank of an uncertain record is the smallest number k such. Note, the numbering denotes the order of selection. To the best of our knowledge, this is the rst work towards topk linked data query processing.
Introduction traditional databases store relatively static data or solid facts on which queries are executed and answers are reflected on. Topk query processing in uncertain databases mohamed a. However, when uncertainty comes into big data, it calls for new parallel algorithms for efficient query processing on large scale uncertain strings. Like many previous works on topk query processing, e. Subrahmanian department of computer science edgelabeled graphs have proliferated rapidly over the last decade due to the increased popularity of social networks and the semantic web. Topk queries operate on index lists for a querys elementary conditions and aggregate scores for result candidates.
Parallel top k query processing on uncertain strings. For simple databases we design dynamicprogramming based algorithms, and for general databases we show polynomialtime reductions to the simple cases. Query processing over uncertain data is very important in many applications due to the existence of uncertainty in realworld data. However, only few works 3, 19, 20 tried to solve the time complexity of top krank queries algorithms. This is because when the exact utility function of a user is known, each topk query returns a set of k tuples from the. Focusing on the singlealternative case, the new algorithms are orders of magnitude faster. Introduction uncertain databases have received a lot of attention recently due to the large number of applications that require management of uncertain andor. The interplay between score and uncertainty makes traditional techniques inapplicable. Topk processing connects to many database research areas including query optimization, indexing methods and query languages. A rank threshold topk query retrieves the records whose pranks.
Parallel top k query processing on uncertain strings using. To the best of our knowledge, this is the rst work towards top k linked data query processing. For example, we demonstrate that for a fixed k the time complexity of topk query evaluation is as low as linear, under the assumption that probabilistic databases are simple and scoring. Nov 20, 2015 the top k query on uncertain data set has been a very hot topic these years, and there have been many studies on uncertain top k queries. Previously, top k query processing is studied in the middleware scenario or in rdbms in a piecemeal fashion, i. This is because when the exact utility function of a user is known, each top k query returns a set of k tuples from the. Skyline queries icde01,sigmod06 k regret queries vldb10,sigmod12,icde14 orderbased skyline queries sigmod10 let me state some interesting queries in the literature. In this paper, it is the first attempt to process probabilistic threshold top k queries an important. Towards this goal, we explore the applicability of the skyline operator for efficiently routing top k queries in a large superpeer network. Top k queries that rank results according to some userdefined score are an important tool for exploring large uncertain data sets. D that are expected to dynamically dominate the largest number of uncertain objects with respect to q, for all instance combinations, in the subspace sub q. Topk queries 1 skyline queries 2 topk dominating queries 3 2 1 a survey of topk query processing techniques in relational database systems, acm csur, 2008.
However, only few works 3, 19, 20 tried to solve the time complexity of top k rank queries algorithms. Processing topk queries from samples is more challenging. The topk query on uncertain data set has been a very hot topic these years, and there have been many studies on uncertain topk queries. Where order by desc stop after where is any expression that evaluates to an integer value, and is uncorrelated with the rest of the query we refer to queries of this kind as topk queries we use the syntax proposed in ck97 see references on the web site. A survey of topk query processing techniques in relational. Topk queries that rank results according to some userdefined score are an important tool for exploring large uncertain data sets. We introduce new probabilistic formulations for top k queries. Previously, topk query processing is studied in the middleware scenario or in rdbms in a piecemeal fashion, i. In this paper, we propose a rangebased probabilistic top k,l query ptr. Exact processing of uncertain topk queries in multicriteria. Where query constraints order by desc stop after where is any expression that evaluates to an integer value, and is uncorrelated with the rest of the query we refer to queries of this kind as top k queries we use the syntax proposed in ck97 see references on the web site.
To the best of our knowledge, very few works refer to uncertain topk range query processing. Therefore, we present an efficient algorithm to processing top k query in the first window which can be treated as a static database d. Towards this goal, we explore the applicability of the skyline operator for efficiently routing topk queries in a large superpeer network. Ieee 20172018 data mining projects in java iris solutions. Keywords uncertain database, ranking queries, sliding window, possible world, topk query. Topk query processing techniques in uncertain databases. An efficient algorithm for krank queries on large uncertain. The main contribution is to change the iteration on instances of objects one by one into iterating all the instances of objects from the superior to the. Probabilistic topk range query processing for uncertain databases and skyline range query 15. In this paper, we present a novel approach, called speerto, for topk query processing in largescale peertopeer networks, where the dataset is horizontally distributed over the peers. Topk query processing in uncertain databases abstract.
Uncertainty in these studies pertains to the data, not to the weight vector. In particular, efficient topk processing in domains such as the web, multimedia search, and distributed systems has shown a great impact on performance. We also discuss the classification of top k query processing techniques in relational databases with different design dimensions. Probabilistic topk range query processing for uncertain databases 1117. Best position algorithms for efficient topk query processing. Topk processing in uncertain databases is semantically and computationally different from traditional topk pro cessing. In the literature, there is another definition of top k rank queries which is the uncertain k ranks query u k ranks, where each tuple in the result is the most probable tuple to. In this paper we introduce new probabilistic formulations for topk queries.
Abstract topk query processing is an important building block for. As shown in figure 1b, the rank probability information used to obtain query answers can also be evaluate quality scores. Toptop topk queries on sql databasesk queries on sql. On efficient topk query processing in highly distributed. We also propose the bpa2 algorithm, which is much more efficient than bpa. E cient query evaluation using a twolevel retrieval process. Efficient processing of topk queries in uncertain databases. When we have a random sample of the records, the natural estimator is the result of.
In this thesis, we present a comprehensive framework, called mtops for multiple topk optimized processing system. Probabilistic topk ranking is an important and wellstudied query operator in uncertain databases. They are thus not suitable for handling large numbers of such simultaneous topk queries due to their unsustainable resource demands. We introduce new probabilistic formulations for topk queries. Today, uncertainty is commonplace in data management scenarios dealing with data integration, sensor readings, information extraction from unstructured sources, and whenever information is manually entered and therefore prone to inaccuracy or partiality. Uncertain data arises in a number of domains, including data integration and sensor networks. Ke yi, feifei li, divesh srivastava, and george kollios. When a web page is accessed by a client, a server increases a local hit counter by one. Existing studies on top k queries can be divided into three big categories. The interplay between score and uncertainty in formationmakestraditionaltopk processingtechniquesin applicable to uncertain databases. Top k queries are used when the exact preferenceutility function of a user is known. Use similar, previously instantiated queries use previous queries to model the correlations between attributes 25 topk processing using views ranking views. Efficient topk query algorithms using density index.
Top k query processing in uncertain databases mohamed a. Crowd sourcing for topk query processing over uncertain datam. In particular, efficient top k processing in domains such as the web, multimedia search, and distributed systems has shown a great impact on performance. Top k queries on certain databases with uncertain utility functions our work other queries. In this survey, we describe and classify top k processing techniques in relational databases. Topk queries are used when the exact preferenceutility function of a user is known.
We discuss different design dimensions in the current techniques including query models, data. Query processing over uncertain databases synthesis. Probabilistic databases synthesis lectures on data management. In the last decade there have been several studies on topk queries in uncertain databases. Topk queries on certain databases with uncertain utility functions our work other queries. In the algorithm, we first sort the l tuples t t t 12,, l in.
Probabilistic topk range query processing for uncertain. Given a ddimensional uncertain database d, a query point q, and a userspecified subspace sub q, a probabilistic topk dominating query in the subspace subptd retrieves k uncertain objects t. Abstract topk query processing in noseong park, doctor of. In this paper, we introduce the topk query processing in relational database system. Bottomup algorithm, which is one of the two probabilistic topk query algorithms, was improved.
In this paper, we present a novel approach, called speerto, for top k query processing in largescale peertopeer networks, where the dataset is horizontally distributed over the peers. Optimizing distributed topk queries on uncertain data. Then, linked data query processing can be modeled as a treestructured plan as exempli ed in fig. In this paper we intro duce new probabilistic formulations for topk queries. Top k query processing in edgelabeled graph data noseong park, doctor of philosophy, 2016 dissertation directed by. Topk processing in uncertain databases is semantically and computationally different from traditional topk processing. One of the wellstudied problems in uncertain databases is the evaluation of topk queries that have more complex semantics than in exact databases. As several recent papers have observed, the semantics of. Therefore, we present an efficient algorithm to processing topk query in the first window which can be treated as a static database d.
Second, a top k,l query returns the topl uncertain records whose probabilities of being ranked among topk are the largest. Distributed topk query processing on multidimensional. Ieee java projects sd pro engineering solutions pvt ltd. We propose bpa algorithm that is much more efficient than ta. When the complete data set is observed, we can compute the frequency of each value and take the topk most frequent values.
Topk query processing is an important building block for ranked retrieval, with applications ranging from text and data integration to distributed aggregation of network logs and sensor data. They are thus not suitable for handling large numbers of such simultaneous top k queries due to their unsustainable resource demands. An efficient algorithm for topk queries on uncertain data. Top \k \ query is an important and essential operator for data analysis over string collections. The interplay between score and uncertainty informationmakestraditionaltopk processingtechniquesinapplicable to uncertain databases. Keywords uncertain database, ranking queries, sliding window, possible world, top k query. Toptop topk queries on sql databasesk queries on sql databases. In this thesis, we present a comprehensive framework, called mtops for multiple top k optimized processing system. In this book, we start from the data models for imprecise and uncertain data, move on to defining different semantics for queries on uncertain data, and finally discuss the advanced query processing techniques for various probabilistic queries in uncertain databases. As several recent papers have observed, the semantics of top k queries on uncertain data can be. Citeseerx document details isaac councill, lee giles, pradeep teregowda. The main objective of top k query processing is to return the k highest ranked results quickly and efficiently.
For example, for the uniform distribution pair, the ptr query time approaches 2,500 seconds for the size of database of 512k, while the time is under 1 seconds for 16k. Distributed topk query processing on multidimensional data. Topk query processing in edgelabeled graph data noseong park, doctor of philosophy, 2016 dissertation directed by. The following examples illustrate realworld scenarios where ef. Continuous subgraph pattern search over certain and uncertain graph streams. The number of accesses done by bpa2 can be up to m. Scalable query processing in probabilistic databases. A candidate filtering mechanism for fast topk query. Our search for uncertain top k query answers starts from an empty state with length 0 and ends at a.
Abstract topk query has been widely studied recently in many applied fields. Indexaccess optimized topk query processing holger bast debapriyo majumdar ralf schenkel martin theobald gerhard weikum maxplanckinstitut f. Uncertain top k query processing in distributed environments. Top k processing in uncertain databases is semantically and computationally different from traditional top k processing. Therefore, if a user wants to obtain a query answer and quality score at the same time, computing the score incurs little overhead. One important query type in the uncertain database is called probabilistic ranked prank query, which retrieves uncertain objects that are expected to have the ith rank with the highest probability, for 1. Bottomup algorithm, which is one of the two probabilistic top k query algorithms, was improved. Topkqueries received increasing interest in relational databases recently 19, mainly as a way to integrate the imprecise query answering semantics of information retrieval with the highly structured storage and rep. Highlights we propose two new algorithms for processing topk queries over sorted lists. In the literature, there is another definition of top krank queries which is the uncertain kranks query ukranks, where each tuple in the result is the most probable tuple to. In proceedings of the 32th international conference on very large data bases, 2006. In this survey, we describe and classify topk processing techniques in relational databases. Distributed topk query processing motivating example assume that we have a cluster of n5 servers.
We show that in a linked data setting, more detailed score information is available. Third, the prank of an uncertain record is the smallest number k such that the record takes a probability of at least p to be ranked in the topk list. Preference query processing over multidimensional data topk queries 1 skyline queries 2 topk dominating queries 3 2 1 a survey of topk query processing techniques in relational database systems, acm csur, 2008. On the semantics and evaluation of topk queries in probabilistic databases. The interplay between score and uncertainty information makes traditional topk processing techniques inapplicable to uncertain databases. Since processing topk query in d with length l requires enumerating all the 2l possible worlds in pw, it takes large amount computation time. Probabilistic top k range query processing for uncertain. In the last decade there have been several studies on top k queries in uncertain databases.
In this paper, it is the first attempt to process probabilistic threshold topk queries an important. Existing studies on topk queries can be divided into three big categories. Citeseerx topk query processing in uncertain databases. Efcient processing of topk queries in uncertain databases. Probabilistic databases synthesis lectures on data. Query processing over uncertain databases has played an increasingly important role in applications like multicriteria decision making, data cleansing, and so on. However, the quality of top k results might be heavily affected by. The main objective of topk query processing is to return the k highest ranked results quickly and efficiently. Unfortunately, most of the existing algorithms only consider centralized processing environments, and they are not suitable for the largescale data.
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