book

XQuery: The XML Query Language

by Michael Brundage

February 2004

Intermediate to advanced

544 pages

9h 55m

English

Addison-Wesley Professional

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Dedication
Who Should Read This Book?OrganizationResourcesAcknowledgments
1.1. Introduction1.2. Getting Started1.3. Notational Conventions1.4. Why XQuery?1.4.1. Query Languages Versus Programming Languages1.4.2. XQuery Versus XPath, XSLT, and SQL1.5. Documents and Databases1.6. Typed and Untyped Data1.6.1. XML Schema Redux1.6.2. The Types You Need1.6.3. The Types You Don't Need1.7. A Sample Query1.8. Processing Model1.9. Comments and Whitespace1.10. Prolog1.11. Constants1.11.1. Boolean Constants1.11.2. String Constants1.11.3. Numeric Constants1.11.4. Other Constants1.12. XML1.13. Built-in Functions1.14. Operators1.14.1. Logic Operators1.14.2. Arithmetic Operators1.14.3. Text Operators1.14.4. Comparison Operators1.15. Paths1.16. Variables1.17. FLWOR1.18. Error Handling1.19. Conclusion1.20. Further Reading
2.1. Introduction2.2. An Overview of XML Data Models2.2.1. Two Examples2.2.2. The Document Object Model (DOM)2.2.3. The XPath 1.0 Data Model2.2.4. The XML Information Set (Infoset)2.2.5. The Post-Schema-Validation Infoset (PSVI)2.2.6. The XQuery Data Model2.3. Structure of the XQuery Data Model2.3.1. Items and Sequences2.3.2. Atomic Values2.3.3. Nodes2.4. Atomic Types2.4.1. Untyped Data2.4.2. Boolean Types2.4.3. Numeric Types2.4.3.1. Numerics Background2.4.3.2. XQuery Numeric Types2.4.4. String Types2.4.5. Calendar Types2.4.6. Qualified Name Type2.4.7. Other Types2.5. Node Kinds2.5.1. Kind, Identity, and Order2.5.2. Hierarchy2.5.3. Node Name2.5.4. Node Type and Values2.5.5. Other Node Properties2.6. Common Type Conversions2.6.1. Atomization2.6.2. Effective Boolean Value2.6.3. Sequence Type Matching2.6.3.1. Type Matching Algorithm2.6.4. Subtype Substitution2.6.5. Numeric Type Promotion2.7. Conclusion2.8. Further Reading
3.1. Introduction3.2. Paths3.2.1. Beginnings3.2.2. Axes3.2.3. Node Tests3.2.3.1. Name Tests3.2.3.2. Node Kind Tests3.2.3.3. Wildcards3.2.4. Other Axes3.2.5. Predicates3.2.5.1. Numeric Predicates3.2.5.2. Boolean Predicates3.2.5.3. Successive and Nested Predicates3.3. Navigation Functions3.4. Navigation Context3.4.1. Input Sequence3.4.2. Focus3.4.3. Variable Declarations3.4.4. Namespace Declarations3.4.5. Function Declarations3.4.6. Collations3.5. Navigation Examples3.6. Navigation Complexities3.6.1. Namespaces3.6.2. Node Identity3.6.3. Other Context Information3.7. Conclusion3.8. Further Reading
4.1. Introduction4.2. Built-in Function Library4.3. Function Invocation4.4. Function Conversion Rules4.5. User-Defined Functions4.6. Recursion4.7. External Functions4.8. Modules4.9. Conclusion

5.1. Introduction5.2. Comparisons5.2.1. Value Comparisons5.2.2. General Comparisons5.2.3. Node Comparisons5.2.4. Sequence and Tree Comparisons5.3. Sequences5.3.1. Constructing Sequences5.3.2. Processing Sequences5.4. Arithmetic5.5. Logic5.6. Query Prolog5.6.1. Version Declaration5.6.2. XML Space Declaration5.6.3. Base URI Declaration5.6.4. Default Collation Declaration5.6.5. Namespace Declarations5.6.6. Global Variable Declarations5.6.7. Module Imports and Declaration5.6.8. Schema Imports and Validation Declaration5.7. Conclusion5.8. Further Reading
6.1. Introduction6.2. FLWOR6.2.1. Compared to SQL6.2.2. Compared to XSLT6.2.3. Introducing Variables6.2.4. Tuples6.3. Quantification6.4. Joins6.5. Comparing Sequences6.5.1. Existential Comparison6.5.2. Memberwise Comparison6.5.3. Universal Comparison6.6. Sorting6.7. Grouping6.8. Conclusion6.9. Further Reading
7.1. Introduction7.2. Element Nodes7.2.1. Direct Element Constructor7.2.2. Computed Element Constructor7.3. Attribute Nodes7.3.1. Direct Attribute Constructors7.3.2. Computed Attribute Constructors7.4. Text Nodes7.5. Document Nodes7.6. Comment Nodes7.7. Processing Instruction Nodes7.8. Namespace Nodes7.9. Composition7.10. Validation7.11. Element and Attribute Content7.11.1. Character Escapes7.11.2. Whitespace7.11.3. Content Sequence7.11.3.1. Attribute Content7.11.3.2. Element Content7.12. Conclusion7.13. Further Reading
8.1. Introduction8.2. The XML Character Model8.2.1. Background8.2.2. Code Points8.2.3. Normalization8.3. Character Encodings8.4. Collations8.5. Text Operators8.6. Text Functions8.7. Conclusion8.8. Further Reading
9.1. Introduction9.2. Cast and Castable9.3. Type Conversion Rules9.3.1. Converting Up and Down the Type Hierarchy9.3.2. Converting Across the Type Hierarchy9.3.2.1. Conversion to/from String9.3.2.2. Conversion to/from Numeric Types and Boolean9.3.2.3. Conversion to/from Calendar Types9.3.2.4. Conversion to/from Binary Types9.4. treat as9.5. instance of and typeswitch9.6. User-Defined Types9.6.1. Schema Imports9.6.2. Typed Content9.6.3. Validation9.7. Conclusion9.8. Further Reading
10.1. Introduction10.2. Style10.2.1. Case10.2.2. Spaces10.2.3. Braces10.2.4. Slice10.2.5. Concise10.3. Idioms10.3.1. Text Idioms10.3.1.1. Reverse a String10.3.1.2. Comma-Separated Values10.3.1.3. Lower-, Upper-, and Title-Case10.3.1.4. Test for ASCII Characters10.3.2. Navigation Idioms10.3.2.1. Select Elements and Attributes Simultaneously10.3.2.2. Navigate Case-Insensitively10.3.2.3. Select Nodes by Type10.3.2.4. Test Whether Two Nodes Are in the Same Tree10.3.2.5. Select All Leaf Elements10.3.2.6. Select All Ancestors10.3.2.7. Select the First Common Ancestor10.3.2.8. Select All Siblings10.3.2.9. Calculate the Maximum Depth10.3.3. Sequence Idioms10.3.3.1. Union, Intersection, and Difference10.3.3.2. Select Every Other Member10.3.3.3. Permutations10.3.4. Type Idioms10.3.4.1. Binary Data10.3.5. Logic Idioms10.3.5.1. Boolean XOR10.3.5.2. Three-Valued Logic10.3.6. Arithmetic Idioms10.3.6.1. IsNaN10.3.6.2. Median10.3.6.3. Rounding Modes10.3.6.4. Random Number Generation10.3.6.5. Factorial10.3.6.6. Square Root10.3.6.7. Complex Numbers10.3.6.8. Linear Algebra10.4. Conclusion10.5. Further Reading
11.1. Introduction11.2. Confusion over Meaning11.2.1. Numbers Like 3.14 Are Decimal, Not Double11.2.2. Predicates Index Sequences, Not Strings11.2.3. not(=) Is Not !=11.2.4. Arithmetic Isn't Associative11.2.5. Predicates + Abbreviated Axes = Confusion11.2.6. Node Sequences Are Different from Node Siblings11.2.7. No Sub-Tree Pruning11.2.8. Type Conversions11.2.9. What's in a Name?11.2.10. FLWOR Doesn't Move the Current Context11.2.11. Nested FLWOR Is Different11.3. Confusion over Syntax11.3.1. Punctuation Is Tricky11.3.2. The <foo/><foo/> Problem11.3.3. XML Numbers Aren't XQuery Numbers11.3.4. Wacky Paths11.4. Conclusion
12.1. Introduction12.2. XQuery Serialization12.2.1. Sequences of Values12.2.2. The Root12.2.3. Serialization Parameters12.3. XQueryX12.4. Conclusion
13.1. Introduction13.2. Common Query Optimizations13.2.1. Lazy Evaluation13.2.2. Early Evaluation13.2.3. Streaming and Database Evaluation13.3. Barriers to Optimization13.3.1. Node Identity13.3.2. Sequence Order13.3.3. Error Preservation13.3.4. Side Effects13.4. Formal Semantics13.5. Conclusion13.6. Further Reading
14.1. Introduction14.2. Potential Changes14.2.1. Namespaces14.2.2. Modules and Prolog14.2.3. Additional Types14.2.4. Simplify, Simplify14.2.5. Built-in Functions14.3. Standards Roadmap14.3.1. Today14.3.2. Tomorrow14.4. XQuery 1.114.5. Data Manipulation14.5.1. XQuery DML14.5.2. SiXDML14.5.3. XUpdate14.6. Full-Text Search14.7. Performance Benchmarks14.8. Conclusion14.9. Further Reading
A.1. IntroductionA.2. OverviewA.3. Node KindsA.4. Atomic TypesA.5. Primitive Type ConversionsA.6. Built-in Atomic Types
B.1. Introductionforletwhereorder byreturn
C.1. Introduction
D.1. IntroductionD.2. OverviewD.3. Advanced RegexpsD.4. Regexp LanguageD.5. Character Properties
E.1. IntroductionE.2. The XQuery GrammarE.3. Reserved KeywordsE.4. Operator Precedence
StandardsWorking Drafts and NotesFurther Reading

Content preview from XQuery: The XML Query Language

Chapter 11. Surprises

Introduction

I once e-mailed an “XPath Quiz” containing six multiple-choice questions about XPath 1.0 to the XML development team at Microsoft. Of those who replied, not one person answered all six questions correctly (although a few got five right). Evidently, XPath is a subtle language filled with hidden complexities, even for the experts who have implemented it! Or as I sometimes exaggerate, “XPath is all special cases.”

As an even larger and more complex language containing most of XPath 2.0 as a subset, XQuery multiplies the surprises. Understanding some of these hidden complexities will illuminate the inner workings of these languages and assist you in mastering their nuances (not to mention any pop quizzes).

This chapter ...