Abstract
Evaluation of twig queries over probabilistic XML is investigated. Projection is allowed and, in particular, a query may be Boolean. It is shown that for a well-known model of probabilistic XML, the evaluation of twigs with projection is tractable under data complexity (whereas in other probabilistic data models, projection is intractable). Under query-and-data complexity, the problem becomes intractable even without projection (and for rather simple twigs and data). In earlier work on probabilistic XML, answers are always complete. However, there is often a need to produce partial answers because XML data may have missing sub-elements and, furthermore, complete answers may be deemed irrelevant if their probabilities are too low. It is shown how to define a semantics that provides partial answers that are maximal with respect to a probability threshold, which is specified by the user. For this semantics, it is shown how to efficiently evaluate twigs, even under query-and-data complexity if there is no projection.
Original language | English |
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Title of host publication | 33rd International Conference on Very Large Data Bases, VLDB 2007 - Conference Proceedings |
Editors | Johannes Gehrke, Christoph Koch, Minos Garofalakis, Karl Aberer, Carl-Christian Kanne, Erich J. Neuhold, Venkatesh Ganti, Wolfgang Klas, Chee-Yong Chan, Divesh Srivastava, Dana Florescu, Anand Deshpande |
Publisher | Association for Computing Machinery, Inc |
Pages | 27-38 |
Number of pages | 12 |
ISBN (Electronic) | 9781595936493 |
State | Published - 2007 |
Event | 33rd International Conference on Very Large Data Bases, VLDB 2007 - Vienna, Austria Duration: 23 Sep 2007 → 27 Sep 2007 |
Publication series
Name | 33rd International Conference on Very Large Data Bases, VLDB 2007 - Conference Proceedings |
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Conference
Conference | 33rd International Conference on Very Large Data Bases, VLDB 2007 |
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Country/Territory | Austria |
City | Vienna |
Period | 23/09/07 → 27/09/07 |
Bibliographical note
Publisher Copyright:Copyright 2007 VLDB Endowment, ACM.