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Overview of XQuery: A Declarative Language for XML Data Queries

XQuery is a high-level, declarative language designed for querying and transforming XML data. Adopted as a W3C standard in January 2007 and developed by Jonathan Robie, Don Chamberlin, and Daniela Florescu, XQuery is strongly typed and functional, promoting a programming style without side effects. It shares features with XSLT and XPath, but offers improved usability and flexibility for transformations. With its XML syntax (XQueryX) and support for the FLWOR expression, XQuery is ideal for small-scale changes within XML documents, facilitating easy XML data handling.

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Overview of XQuery: A Declarative Language for XML Data Queries

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  1. XQuery Leah Andrews

  2. Overview • Queries data stored in XML trees • Declarative • High-level • Functional (no side effects) • Strongly typed • Nodes • Atomic values (integers, strings, booleans)

  3. Origins • Became a W3 standard in January, 2007 • Developed by Jonathan Robie, Don Chamberlin and Daniela Florescu • Compatible with other W3 standards • XML (namespaces, Schema), XSLT, XPath

  4. XQuery v. XSLT • Overlapping capabilities • Share a data model, type system, function library and XPath

  5. XQuery > XSLT • Better usability • More concise • Other languages can be embedded • More Orthogonal • Can be expressed in XML syntax (XQueryX)

  6. XSLT > XQuery • Better for small-scale changes to XML documents • Widespread use • More flexible for transformations

  7. XQuery does NOT support: • Full text search capacity • Updating XML documents or databases • Dynamic typing • Polymorphism

  8. FLWOR • FOR • LET • WHERE • ORDER BY • RETURN

  9. <?xml version="1.0" encoding="ISO-8859-1"?> <class> <students> <student name="Leah"> <studentId>1</studentId> <laptop>MacBook</laptop> <favoritecolor>olive</favoritecolor> </student> <student name="Ian"> <studentId>2</studentId> <laptop>WinBook</laptop> <favoritecolor>orange</favoritecolor> </student> <student name="Kyle"> <studentId>3</studentId> <laptop>Toshiba</laptop> <favoritecolor>orange</favoritecolor> </student> <student name="Chris"> <studentId>4</studentId> <laptop>Gateway</laptop> <favoritecolor>green</favoritecolor> </student> <student name="Stacy"> <studentId>5</studentId> <laptop>Asus</laptop> <favoritecolor>rainbow</favoritecolor> </student> <student name="Tom"> <studentId>6</studentId> <laptop>ZT</laptop> <favoritecolor>black</favoritecolor> </student> <student name="Brad"> <studentId>7</studentId> <laptop>IMB</laptop> <favoritecolor>unknown</favoritecolor> </student> </students> <professors> <professor name="Axel"> <id>8</id> <laptop>MacBook</laptop> <favoritecolor>German</favoritecolor> </professor> </professors> </class>

  10. xquery version "1.0"; <html> <body> <p>All students</p> <ul> { for $x in doc("students.xml")/class/students order by $x/studentId return <li> { $x } </li> } </ul> </body> </html>

  11. xquery version "1.0"; <html> <body> <p>Students with an id less than 5</p> <ul> { for $x in doc("students.xml")/class/students where $x/studentId<5 order by $x/studentId return <li> {data($x/@name)} </li> } </ul> </body> </html>

  12. xquery version "1.0"; <html> <body> <p>Favorite (student) colors</p> <ul> { for $x in doc("students.xml")/class/students/favoritecolor return <li> {data($x)} </li> } </ul> </body> </html>

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