Contents 1 Introduction .................................................................. 1 1.1 XML Data Model ....................................................... 1 1.2 Emergenceof XML Database .......................................... 3 1.2.1 Flat File Storage ............................................... 3 1.2.2 Relational and Object Relational Storage .................... 3 1.2.3 Native Storage of XML Data ................................. 4 1.3 XML Query Languageand Processing ................................ 5 1.4 XML Keyword Search.................................................. 5 1.5 Book Outline ............................................................ 6 References ..................................................................... 7 2 XML Labeling Scheme ...................................................... 9 2.1 IntroducingXML LabelingScheme ................................... 9 2.2 Region EncodingScheme .............................................. 10 2.3 Dewey and Extended Dewey Scheme.................................. 11 2.3.1 Dewey ID Labeling Scheme .................................. 11 2.3.2 ExtendedDewey and FST .................................... 12 2.4 Dynamic Labeling Scheme............................................. 16 2.4.1 Region-Based Dynamic Labeling Scheme................... 17 2.4.2 Pre.x-Based Dynamic Labeling Scheme .................... 18 2.4.3 PrimeLabelingScheme....................................... 19 2.4.4 The EncodingSchemes ....................................... 20 2.5 Summary ................................................................ 31 References ..................................................................... 31 3 XML Data Indexing ......................................................... 33 3.1 IntroducingXML Data Indexing....................................... 33 3.2 IndexesonXMLTreeStructure........................................ 34 3.2.1 DataGuides .................................................... 34 3.2.2 1-Index......................................................... 39 3.2.3 F&B-Index..................................................... 43 ix Contents 3.3 Index Based on XML Sequencing ..................................... 54 3.3.1 PRIX: Indexing and Querying XML Using Pr¡§ufer Sequences .............................................. 54 3.3.2 ViST: A Dynamic Index Method for Querying XML Data by Tree Structures ................................ 65 3.3.3 APEX: An AdaptivePath Index for XML Data ............. 75 3.4 Summary ................................................................ 87 References ..................................................................... 88 4 XML Tree Pattern Processing .............................................. 91 4.1 IntroducingXML Tree Pattern Processing ............................ 91 4.2 XML Structural Join .................................................... 92 4.2.1 Tree-MergeJoinAlgorithms.................................. 94 4.2.2 Stack-TreeJoinAlgorithms................................... 97 4.3 XML Holistic Twig Pattern Processing ................................ 103 4.3.1 PathStack ...................................................... 104 4.3.2 TwigStack...................................................... 108 4.3.3 TwigStackList ................................................. 112 4.3.4 TJFast .......................................................... 122 4.3.5 ExperimentalEvaluation...................................... 128 4.4 XML Query Processing Based on VariousStreaming Schemes...... 134 4.4.1 TagCLevelStreamingandPre.x-PathStreaming(PPS).... 135 4.4.2 iTwigJoin Algorithm .......................................... 144 4.5 Summary ................................................................ 155 References ..................................................................... 155 5 Ordered and Generalized XML Tree Pattern Processing ............... 157 5.1 IntroducingOrdered and GeneralizedXML Tree Pattern Processing 157 5.2 XML Ordered Query Processing....................................... 158 5.2.1 Data Model and Ordered Twig Pattern ....................... 159 5.2.2 XML Ordered Query Processing Algorithm................. 160 5.2.3 Analysis of OrderedTJ ........................................ 163 5.2.4 ExperimentalEvaluation...................................... 165 5.3 XML Generalized XML Tree Pattern.................................. 167 5.3.1 GTJFast Algorithm............................................ 168 5.3.2 AnalysisofGTJFast........................................... 171 5.3.3 Experiments ................................................... 173 5.4 ExtendedXML Tree Pattern............................................ 174 5.4.1 ExtendedTree Pattern Query ................................. 176 5.4.2 MatchingCross................................................ 177 5.4.3 Holistic Algorithms ........................................... 183 5.4.4 Experiments ................................................... 193 5.5 Summary ................................................................ 200 References ..................................................................... 200 Contents 6 Effective XML Keyword Search ........................................... 203 6.1 IntroducingEffective XML Keyword Search.......................... 203 6.2 XMLKeywordSearchSemantics...................................... 204 6.2.1 LCA and the Meet Operator .................................. 205 6.2.2 MLCA and MLCAS .......................................... 205 6.2.3 SLCA .......................................................... 206 6.2.4 GDMCT ....................................................... 207 6.2.5 ICA (Interested Common Ancestor) and IRA (InterestedRelatedAncestors)................................ 209 6.2.6 ELCA (Exclusive Lowest Common Ancestor) .............. 210 6.2.7 VLCA (Valuable Lowest Common Ancestor) ............... 210 6.2.8 MCN ........................................................... 211 6.2.9 MeaningfulSLCA............................................. 211 6.2.10 LCEA (Lowest Common Entity Ancestor) .................. 213 6.2.11 MLCEA (MeaningfulLCEA) ................................ 213 6.3 XML Keyword Search Algorithms..................................... 213 6.3.1 DIL (Dewey InvertedList) Query Processing Algorithm ... 213 6.3.2 The Stack Algorithm .......................................... 216 6.3.3 Basic Multiway-SLCA Algorithm (BMS) ................... 218 6.3.4 IncrementalMultiway-SLCA Algorithm(IMS) ............. 220 6.3.5 IndexedStack Algorithm...................................... 221 6.3.6 Stack-Based Query Re.nement Algorithm .................. 223 6.4 XML Keyword Search Ranking Strategy.............................. 224 6.4.1 TF*IDF Cosine Similarity .................................... 225 6.4.2 Data Model .................................................... 226 6.4.3 XML TF&DF.................................................. 226 6.4.4 Inferringthe Node Type to Search For ....................... 227 6.4.5 Inferringthe Node Types to Search Via ...................... 227 6.4.6 Capturing KeywordCo-occurrence .......................... 228 6.4.7 Relevance-OrientedRanking ................................. 228 6.5 Summary ................................................................ 231 References ..................................................................... 231 7 XML Keyword Pattern Re.nement........................................ 233 7.1 IntroducingXML Keyword Pattern Re.nement....................... 233 7.2 Related Work............................................................ 237 7.3 Preliminaries ............................................................ 238 7.3.1 MeaningfulSLCA............................................. 238 7.3.2 Re.nementOperations........................................ 240 7.4 Ranking of Re.ned Queries ............................................ 242 7.4.1 Similarity Score of a RQ...................................... 243 7.4.2 DependenceScore of a RQ ................................... 245 7.5 Exploringthe Re.ned Query ........................................... 247 7.5.1 ProblemFormulation.......................................... 247 7.5.2 Subproblems................................................... 247 xii Contents 7.5.3 Notations....................................................... 247 7.5.4 Initialization ................................................... 248 7.5.5 RecurrenceFunction .......................................... 248 7.5.6 Time Complexity.............................................. 248 7.6 Content-Aware Query Re.nement ..................................... 249 7.6.1 Partition-Based Algorithm.................................... 250 7.6.2 Short-ListEagerAlgorithm................................... 253 7.7 Experiments ............................................................. 256 7.7.1 Equipment ..................................................... 256 7.7.2 Dataset and Query Set......................................... 256 7.7.3 Ef.ciency ...................................................... 257 7.7.4 Scalability...................................................... 259 7.7.5 Effectivenessof Query Re.nement........................... 261 7.8 Summary ................................................................ 264 References ..................................................................... 264 8 LCRA, XML Keyword Search System, and LotusX, Graphical Query Processing System ....................................... 267 8.1 Introductionof LCRA and LotusX..................................... 267 8.2 LCRA: Search Semantics............................................... 268 8.2.1 SLCA and LRA ............................................... 268 8.2.2 Backgroundand Data Model ................................. 269 8.2.3 SearchSemantics.............................................. 270 8.3 LCRA, System Architecture, and Ranking Techniques............... 272 8.3.1 Tree Model..................................................... 272 8.3.2 RankingTechniques........................................... 273 8.3.3 SystemArchitecture........................................... 274 8.3.4 OverviewofOnlineDemoFeatures.......................... 274 8.4 A Position-Aware XML Graphical Search System with Auto-completion................................................... 276 8.4.1 System Features ............................................... 276 8.4.2 LotusX:ArchitectureandAlgorithms........................ 278 8.5 Summary ................................................................ 282 References ..................................................................... 283 9 Summary and the Road Ahead ............................................. 285 9.1 Summary of This Book ................................................. 285 9.2 Future Work ............................................................. 286 9.2.1 Full-FledgedXML Query Engine ............................ 286 9.2.2 Directed Graph XML Model.................................. 286 9.2.3 ExtendedDewey Labeling Scheme for OrderedQuery ..... 287 9.2.4 IndexStructure Based on TJFast ............................. 287 9.2.5 MapReduce-BasedXML Twig Pattern Matching ........... 288 References ..................................................................... 288 Index ............................................................................... 289
