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Adaptive Processing of Top-k Queries in XML
Amelie Marian , Sihem Amer-Yahia
Nick Koudas , Divesh Srivastava
Proceedings of the 21st International Conference on Data Engineering (ICDE2005)
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XML<book> <title>wodehouse</title> <info> <publisher> <name>psmith</name> <location>london</location> </publisher> <isbn>1234</isbn> </info> <price>48.95</price></book>
<book> <title>wodehouse</title> <publish> <name>psmith</name> <location>london</location> </publish> <info> <isbn>1234</isbn> </info></book>
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XML
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XML
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XML XPath
pc : parent – child
ad : ancestor-descendant
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Scoring Function
The traditional tf*idf function is defined in IR.tf : term frequency : quantifies the relative importance of a keyword in an individual document.idf : inverse document frequency : quantifies the relative importance of an individual keyword in the collection of documents.
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Scoring Function
XML unlike traditional IR
An answer to an XPath query need not be an entire document, but can be any node in a document.
An XPath query consists of several predicates linking the returned node to other query nodes, instead of simply “keyword containment in the document” (as in IR).
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Scoring FunctionXPath Component Predicates
XPath query Q
q0 : query answer node
qi , 1 <= i <= l : other query nodes
p( q0 , qi ) : XPath axis between query nodes q0 and qi , i>=1
PQ (component predicates of Q): set of predicates {p(q0,qi)}, 1<= i <= l
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Scoring Function
XML idf
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Scoring Function
XML tf
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Scoring Function
XML tf*idf Score
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Whirlpool Architecture
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Whirlpool Architecture
Servers and Server Queues
Top-k Set
Router and Router Queue
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Server Predicates Generation
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Whirlpool
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Scheduling between components
Single-threaded
Multi-threaded
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Experimental
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Conclusion
Whirlpool , an adaptive evaluation strategy for computing exact and approximate top-k answers of XPath queries.
We are investigating new directions such as increasing the number of threads per server for maximal parallelism.