In proceedings of the 32th international conference on very large data bases, 2006. Best position algorithms for efficient top k query processing. The top k multi query distinguishes itself from the traditional top k query in. A survey of topk query processing techniques in relational. Top k processing in uncertain databases is semantically and computationally different from traditional top k processing. We use the term object to denote a multidimensional tuple in the input data stream. It deals with multiple data types and finds the information in the order of relevance between the query and the object. In order to support top k queries in our unified framework, we have developed very efficient waveletbased data synopses and algorithms that approximate the top k results with most operations occurring in the wavelet. Unified framework for topk query processing in peertopeer. In this paper, we propose the first efficient and provably secure top k query processing. A parallel processing method for moving topk spatial. The interplay between score and uncertainty makes traditional techniques inapplicable. Disregard index lists with low idf below given threshold.
Use similar, previously instantiated queries use previous queries to model the correlations between attributes 25 top k processing using views ranking views. Top k queries operate on indexlists for a query s elementary conditions and aggregate scores for result can. To e ciently analyze and understand large array data, the support of top k. Pdf semantic query routing and distributed topk query. Topk query processing in the appa p2p system 1 core. In the survey of uncertain data algorithms and applications by charu c. Array databases manage extremely large multidimensional array data, and therefore, it is di cult to understand data intuitively and extract important regions. Sum, max, min, count, product, minimize some cost metric associated with the retrieval of the correct answers e. This paper presents a comprehensive overview of the topx search engine.
However, there is very limited work on how to securely process top k ranking queries over encrypted databases in the cloud. The proposed schemes are built upon symmetric cryptographic primitives and enable the network owner to detect any incorrect top k query results. Abstract top k 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. In this paper, we propose a fully distributed algorithm for executing top k queries in the context of the appa atlas peertopeer architecture data management system. The objects that participate in the top k results of a given window are referred to as the top k elements of that window. Query processing would mean the entire process or activity which involves query translation into low level instructions, query optimization to save resources, cost estimation or evaluation of query, and extraction of data from the database. Topk query processing in uncertain databases citeseerx. Top k join query processing over ranked inputs has been studied in literature e. Citeseerx document details isaac councill, lee giles, pradeep teregowda. Which webpage has the highest hit rate scoreo i across all servers.
Abstract topk query processing in noseong park, doctor of. Previous distributed top k query processing algorithms have restrictive assumptions about how the data is partitioned among the peers in the system 11,12. We introduce new probabilistic formulations for topk queries. Top k queries are attractive for users in p2p systems with very large numbers of peers but difficult to support efficiently. Opposed to top k queries where specific ranking functions and criteria are used, skyline queries assume that every user has a series of preferences over the attributes of data. We show that in a linked data setting, more detailed score information is available. Pdf topk query processing in uncertain databases mohamed. It terminates query execution as soon as it can safely determine the k top ranked result elements according to a. Top kqueries 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. 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.
The main difference compared to traditional topk queries is that the score of each data object is. Which webpage has the highest number of hits across all servers i. Embedding rankawareness in query processing techniques provides a more ef. Pdf unified framework for topk query processing in peerto. Top k query processing in edgelabeled graph data noseong park, doctor of philosophy, 2016 dissertation directed by. Top k query processing on encrypted databases with strong security guarantees abstract.
Approximate importance query aiq, our third model, allows partial and inexact matchings and returns top k of them with a userspecified approximation terms and scoring functions. For scheduling index scans, give priority to index lists that are short and have high idf. In this paper, we propose a novel approach for processing spatial preference queries ef. Distributed topk query processing motivating example assume that we have a cluster of n5 servers. Instead of computing all results, top k query processing approaches produce only the \best kresults 8. There are many applications handling huge amounts of geotagged data, such as twitter and flickr, that can benefit from this query. Generic topk query processing with breadthfirst strategies. Top k processing connects to many database research areas including query optimization, indexing methods, and query languages. The following examples illustrate realworld scenarios where ef. Topx is a top k retrieval engine for text and semistructured data. As shown in 7, the con denceaware solution not only secures the query answering quality but also minimizes the crowdsourcing cost. 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. Top k query processing in uncertain databases mohamed a. To the best of our knowledge, this is the first paper proposing parallel algorithms to process topk.
Determine k objects with the highest overall score. A candidate filtering mechanism for fast topk query. The topk query is define as given a database d of m objects, each of which is. Efficient processing of top k queries is a crucial requirement in many interactive environments that involve massive amounts of data. Stop adding candidates to the queue if we run out of memory. Scalable and efficient processing of topk multipletype.
We introduce new probabilistic formulations for top k queries. Top k query processing is the task of identifying the top kscored documents, out of a collection of documents, for a given query q and a given scoring function sq. Topk query processing techniques in uncertain databases. To find the k highest ranked answers to a user defined aggregate similarity scoring function. Top k queries are used when the exact preferenceutility function of a user is known. Secure top k query processing in unattended tiered sensor networks rui zhang, jing shi, yanchao zhang, and xiaoxia huang, ieee transactions on vehicular technology, vol. When a web page is accessed by a client, a server increases a local hit counter by one. Bottomup algorithm, which is one of the two probabilistic top k query algorithms, was improved. Citeseerx topk query processing in uncertain databases. 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. Taking this into account skyline queries deflect from the strict ranking approach of top k queries and directed to an approach that is more understandable by hummans. Unified framework for topk query processing in peerto. Topk queries operate on index lists for a querys elementary conditions and aggregate scores for result candidates. Best position algorithms for efficient topk query processing.
It empirically demonstrates the advantages of the proposed runtime causal inference mechanism and the query processing algorithms in terms of the. Secure topk query processing in unattended tiered sensor. Query model, data access methods, implementation level, query and data uncertainty, ranking functions 9. The proposed schemes are built upon symmetric cryptographic primitives and enable the network owner to detect any incorrect topk query results. Probabilistic top k query processing stanford university. Query processing advanced database management system. To the best of our knowledge, this is the rst work towards top k linked data query processing. In this survey, we describe and classify top k processing techniques in relational databases. Concerns about privacy in outsourced cloud databases have grown recently and many efficient and scalable query processing methods over encrypted data have been proposed. Stop scanning a particular list if the local scores in it become low. Globa top k method minimize the search space by twolevel method. A naive implementation of top k is to sort all of the items and then return the first k, but this does much more work than needed.
In this paper, we introduce the top k query processing in relational database system. In this survey, we discuss the stateoftheart topk query processing techniques in reacm journal name, vol. The core of the bottomup algorithm is the iteration on the three courses of bounding, pruning,and refining towards the objects and instances. Due to this complexity, existing solutions are costly in terms of both ios and execution time 16,17. Topk query processing in uncertain databases cheriton school. In such systems each peer is a database management system in itself. In particular, efficient top k processing in domains such as. When we have a random sample of the records, the natural estimator is the result of performing the same action on the sample.
Progressive topk subarray query processing in array. Topk query example assume that we have a cluster of n5 webservers. Topk query processing on encrypted databases with strong. A survey of topk query processing techniques in relational database systems ihab f. Scan all m index lists until k k docs have been found that appear in all lists. Processing top k queries from samples is more challenging. Efficient processing of topk spatial keyword queries. Pdf a survey of topk query processing techniques in. When the complete data set is observed, we can compute the frequency of each value and take the top k most frequent values. The space of possible relaxations is potentially too large to fully explore and users are typically interested in only top k results, so such query engines use top k algorithms for query processing. More specifically, we develop a novel unified top k query processing framework supporting various types of data partitioning. A survey of topk query processing techniques in relational database. When we have a random sample of the records, the natural estimator is the result of.
Maxscore 25, 23, wand 2, and bmw 8, are some representative dynamicpruning algorithms for the top k processing task. Hence, sorting the join results becomes necessary to produce the top k answers. Previously, top k query processing is studied in the middleware scenario or in rdbms in a piecemeal fashion, i. A common operation in many data analytics workloads is to find the top k items, i. Hence, sorting the join results becomes necessary to produce the topk answers. This is based on the observation that results may vary in \relevance which can be quanti ed via a ranking function, and users, especially on the web, are often interested in only a few relevant results. The main objective of top k query processing is to return the k highest ranked results quickly and efficiently. Supporting queries over dispersed data stored in largescale distributed systems, such as peertopeer networks, naturally calls for ranked retrieval in order to effectively focus on the most relevant ie, top k results.
Probabilistic top k query processing probsorted query q, indexlists l, rebuildperiod r, queuebound b. In the fourth model called probabilistic importance query piq, a query consists of several subblocks. Given a spatial location and a set of keywords, a top k spatial keyword query returns the k best spatiotextual objects ranked according to their proximity to the query location and relevance to the query keywords. 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. A survey of topk query processing techniques in relational database systems article pdf available in acm computing surveys 404. Many algorithms for topk query processing with ranking predicates have been proposed, but little effort has been directed toward genericity, i. General pruning and indexaccess ordering heuristics. Tuple scores and probabilities interplay to decide on meaningful topk answers. Processing topk queries using the nave algorithm is very expensive for large databases, as it requires sorting a large. In order to support top k queries in our unified framework, we have developed very efficient waveletbased data synopses and algorithms that approximate the top k results with most operations occurring in the wavelet coefficient domain.
Recent ir extensions to xml query languages such as xpath 1. The efforts can be classified into two categories according to the index structures used. Various data types such as spatial, textual, and relational data types can be used for the top k multi query. Top k query processing in various elds has been extensively studied.
Requirements for widely distributed information systems supporting virtual organizations have given rise to a new category of peertopeer p2p systems called schemabased. Exhaustive search and reduced search early termination, to continuously predict the top k next effects over event streams. Documents are usually scored based on an estimation of their relevance to the query. A parallel processing method for moving topk spatial keyword. We also discuss the classification of top k query processing techniques in relational databases with different design dimensions. To find an efficient query execution plan for a given sql query which would minimize the cost.
Each server maintains locally the same m5 webpages. In this survey, we discuss the stateoftheart top k query processing techniques in reacm journal name, vol. Efficient topk query processing on massively parallel. There have been many research efforts on top k spatial keyword query processing 3, 810, 12, 20, 21. Stop scanning ith index list when highi effective when total score of topk results is dominated by r firstk heuristics.
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