Keyword search in databases

155 Pages·2010·1.125 MB·English

by  Jeffrey Xu Yu, Lu Qin, Lijun Chang

Keyword Search in Databases

Synthesis Lectures on Data
Management
Editor
M.TamerÖzsu
KeywordSearchinDatabases
JeffreyXuYu,LuQin,andLijunChang
2010
Copyright© 2010byMorgan&Claypool
Allrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedin
anyformorbyanymeans—electronic,mechanical,photocopy,recording,oranyotherexceptforbriefquotationsin
printedreviews,withoutthepriorpermissionofthepublisher.
KeywordSearchinDatabases
JeffreyXuYu,LuQin,andLijunChang
www.morganclaypool.com
ISBN:9781608451951 paperback
ISBN:9781608451968 ebook
DOI10.2200/S00231ED1V01Y200912DTM001
APublicationintheMorgan&ClaypoolPublishersseries
SYNTHESISLECTURESONDATAMANAGEMENT
Lecture#1
SeriesEditor:M.TamerÖzsu
SeriesISSN
SynthesisLecturesonDataManagement
ISSNpending.
Keyword Search in Databases
Jeffrey XuYu,Lu Qin,and Lijun Chang
ChineseUniversityofHongKong
SYNTHESISLECTURESONDATAMANAGEMENT#1
M
&C Morgan &cLaypool publishers
ABSTRACT
Ithasbecomehighlydesirabletoprovideuserswithflexiblewaystoquery/searchinformationover
databasesassimpleaskeywordsearchlikeGooglesearch.
Thisbooksurveystherecentdevelopmentsonkeywordsearchoverdatabases,andfocuseson
findingstructuralinformationamongobjectsinadatabaseusingasetofkeywords.Suchstructural
information to be returned can be either trees or subgraphs representing how the objects, that
containtherequiredkeywords,areinterconnectedinarelationaldatabaseorinanXMLdatabase.
Thestructuralkeywordsearchiscompletelydifferentfromfindingdocumentsthatcontainallthe
user-givenkeywords.Theformerfocusesontheinterconnectedobjectstructures,whereasthelatter
focusesontheobjectcontent.
The book is organized as follows. In Chapter 1, we highlight the main research issues on
thestructuralkeywordsearchindifferentcontexts.InChapter2,wefocusonsupportingstructural
keyword search in a relational database management system using the SQL query language.We
concentrate on how to generate a set of SQL queries that can find all the structural information
among records in a relational database completely,and how to evaluate the generated set of SQL
queriesefficiently.InChapter3,wediscussgraphalgorithmsforstructuralkeywordsearchbytreating
anentirerelationaldatabaseasalargedatagraph.InChapter4,wediscussstructuralkeywordsearch
inalargetree-structuredXMLdatabase.InChapter5,wehighlightseveralinterestingresearchissues
regardingkeywordsearchondatabases.
The book can be used as either an extended survey for people who are interested in the
structuralkeywordsearchorareferencebookforapostgraduatecourseontherelatedtopics.
KEYWORDS
keywordsearch,interconnectedobjectstructures,relationaldatabases,XMLdatabases,
datastream,rank
To my wife, Hannah
my children, Michael and Stephen
Jeffrey Xu Yu
To my wife, Michelle
my parents, Hanmin and Yaping
Lu Qin
To my parents, Qiyuan and Yumei
Lijun Chang

ix
Contents
Preface......................................................................xi
1 Introduction.................................................................1
2 Schema-BasedKeywordSearchonRelationalDatabases........................3
2.1 Introduction ...............................................................3
2.2 CandidateNetworkGeneration.............................................12
2.3 CandidateNetworkEvaluation.............................................21
2.3.1 GettingAllMTJNTsinaRelationalDatabase 22
2.3.2 GettingTop-k MTJNTsinaRelationalDatabase 29
2.4 OtherKeywordSearchSemantics...........................................34
3 Graph-BasedKeywordSearch ............................................... 45
3.1 GraphModelandProblemDefinition.......................................45
3.2 PolynomialDelayandDijkstra’sAlgorithm ..................................49
3.3 SteinerTree-BasedKeywordSearch.........................................53
3.3.1 BackwardSearch 53
3.3.2 DynamicProgramming 55
3.3.3 EnumeratingQ-subtreeswithPolynomialDelay 57
3.4 DistinctRoot-BasedKeywordSearch .......................................69
3.4.1 BidirectionalSearch 69
3.4.2 Bi-LevelIndexing 71
3.4.3 ExternalMemoryDataGraph 73
3.5 Subgraph-BasedKeywordSearch...........................................76
3.5.1 r-RadiusSteinerGraph 76
3.5.2 Multi-CenterInducedGraph 78
x CONTENTS
4 KeywordSearchinXMLDatabases .......................................... 83
4.1 XMLandProblemDefinition..............................................83
4.1.1 LCA,SLCA,ELCA,andCLCA 84
4.1.2 ProblemDefinitionandNotations 87
4.2 SLCA-BasedSemantics...................................................88
4.2.1 PropertiesofLCAandSLCA 89
4.2.2 EfficientAlgorithmsforSLCAs 90
4.3 IdentifyMeaningfulReturnInformation.....................................98
4.3.1 XSeek 99
4.3.2 MaxMatch 102
4.4 ELCA-BasedSemantics..................................................106
4.4.1 EfficientAlgorithmsforELCAs 107
4.4.2 IdentifyingMeaningfulELCAs 111
4.5 OtherApproaches........................................................112
5 OtherTopicsforKeywordSearchonDatabases..............................115
5.1 KeywordSearchAcrossDatabases.........................................115
5.1.1 SelectionofDatabases 115
5.1.2 AnsweringKeywordQueriesAcrossDatabases 119
5.2 KeywordSearchonSpatialDatabases......................................120
5.2.1 PointsasResult 120
5.2.2 AreaasResult 121
5.3 VariationsofKeywordSearchonDatabases.................................123
5.3.1 ObjectsasResults 123
5.3.2 SubspacesasResults 125
5.3.3 TermsasResults 126
5.3.4 sqlQueriesasResults 128
5.3.5 SmallDatabaseasResult 129
5.3.6 OtherRelatedIssues 130
Bibliography...............................................................133
Authors’Biographies.......................................................143