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W3C

Get title of books published by Addison-Wesley after 1993. ... Get titles of books published after 1994, but. NOT published by Addison-Wesley. Order the ...

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W3C

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  1. W3C(World Wide Web Consortium) • What is W3C? • An industry consortium, best known for standardizing HTML and XML. • Working Groups create or adopt new “recommendations” • www.w3.org

  2. XML(eXtensible Markup Language) <bib> <book year="1994"> <title>TCP/IP Illustrated</title> <author> <last>Stevens</last> <first>W.</first> </author> <publisher>Addison Wesley</publisher> <price>65.95</price> </book> <book year="1992"> <title> … … </bib>

  3. XQuery – Example 1 Get title of books published by Addison-Wesley after 1993. for $b in doc("XMP/bib.xml")/bib/book where $b/publisher = "Addison-Wesley" and $b/@year > 1993 return $b/title <title>TCP/IP Illustrated</title>

  4. FLWOR Expressions • Basic FLWOR Expression: • For – consider (introduce a variable) • Let – introduce additional variables • Where – filter by conditions • Order by – order the output • Return – build results • Xquery is compositional: any place XML data can go, another { FLWOR } expression can go.

  5. XQuery – Example 2 Get titles of books published after 1994, but NOT published by Addison-Wesley. Order the result in descending order by title. for $b in doc("XMP/bib.xml")/bib/book let $c := $b/publisher where $c != "Addison-Wesley" and $b/@year > 1994 order by $b/title descending return $b/title <title>The Economics of Technology and Content of Digital TV</title><title>Data on the Web</title>

  6. XQuery – Example 3 Join <bib> and <reviews> on <title> and print the title and price. for $b in doc("XMP/bib.xml")/bib/book, $e in doc("XMP/reviews.xml")/reviews/entry where $e/title = $b/title return <titlelist> { $b/title, $e/price } </titlelist> <titlelist> <title>TCP/IP Illustrated</title> <price>65.95</price> </titlelist>

  7. XQuery – Example 4 Get the average price of the books. <results>{ let $prices := doc("XMP/bib.xml")/bib/book/price return <avgprice>{ avg($prices) }</avgprice> }</results> <results> <avgprice>75.45</avgprice> </results>

  8. XQuery – Example 5 Get year (as an attribute) and title of book. (Use a predicate to limit the books to those published by Addison-Wesley.) for $b in doc("XMP/bib.xml")/bib/book, $c in $b[publisher = "Addison-Wesley"] return <book> { $c/@year } { $c/title } </book> <book year="1994"> <title>TCP/IP Illustrated</title> </book><book year="1992"> <title>Advanced Programming in the Unix environment</title> </book>

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