Web Technologies 20072008

1
Web Technologies2007/2008

• Lecture 3b
• XML

New Perspectives on XML, Patrick Carey Ioannis
Ivrissimtzis 14-Mar-2008
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Overview

• Introduction to XML
• XML documents
• CSS for XML

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XML

• XML stands for Extensible Markup Language.
• XML conforms with the standards of the Standard
  Generalized Markup
• Language (SGML).
• An XML document structures information using
  tags. Unlike HTML,
• XML is not restricted into predefined set of
  tags.
• Parsers interpreting XML code and associated
  style sheets are built in
• the main browsers IE and Mozilla.

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Example

• Example Consider the web-site of an online
  bookstore. We would like
• to create records of books, storing the following
  information
• Title
• Author
• Publisher
• Price
• Content Type (Fiction, Nonfiction)
• Format (Paperback, Hardback)
• ISBN

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Example

• The following code shows a possible XML code for
  one book
• ltbookgt
• lttitlegtNight Falllt/titlegt
• ltauthorgtDemille, Nelsonlt/authorgt
• ltpublishergtWarnerlt/publishergt
• ltpricegt26.95lt/pricegt
• ltcontentTypegtFictionlt/contentTypegt
• ltformatgtHardbacklt/formatgt
• ltisbngt0446576638lt/isbngt
• lt/bookgt

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PCDATA and CDATA

• The previous piece of code is a sample of parsed
  character
• data, (PCDATA).
• PCDATA consists of all those characters that XML
  treats as parts of the
• code of XML document
• The XML declaration
• The opening and closing tags of an element
• Empty element tags
• Character or entity references
• Comments

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PCDATA and CDATA

• A CDATA section is a block of text the XML
  processor will interpret only
• as text. The syntax is
• lt! CDATA
• Text block
• gt

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Overview

• Introduction to XML
• XML documents
• CSS for XML

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XML documents

• An XML documents consist of three parts
• The prolog
• The document body
• The epilog
• The prolog provides information about the
  document.
• The documents body contains the documents
  content structured as a tree.
• The epilog contains any final comments or
  processing instructions.

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Prolog

• The first line of the prolog is the XML
  declaration, which tells the
• processor that what follows is written using XML.
  
• The syntax is
• lt?xml versionversion number
  encodingencoding type standaloneyes no ?gt
• A typical declaration would look like
• lt?xml version1.0 encodingUTF-8
  standaloneyes ?gt

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Document body

• The basic blocks of an XML document are the
  elements (tags).
• The syntax of an element is
• ltelement_namegtContentlt/element_namegt
• Example The XML file of a Jazz CD catalogue
  might contain an
• element
• ltArtistgtMiles Davislt/Artistgt

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Document body

• Elements can be nested
• ltCDgtKind of Blue
• ltTRACKgtSo What ((22)lt/TRACKgt
• ltTRACKgtBlue in Green (537)lt/TRACKgt
• lt/CDgt

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Document body

• The elements (and the element types) of an XML
  document create a
• tree structure.
• Example The element types used for the CD
  catalogue can have the
• structure

SPECIALS
TITLE
MESSAGE
CD
PRICEUK
PRICEUS
ARTIST
TRACK
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Document body

• Example (cont.)
• SPECIALS is the root of the tree. It groups
  everything together.
• TITLE contains the title of the catalogue.
• MESSAGE contains some text information about the
  catalogue.
• CD contains information about a CD.
• ARTIST contains the artists name.
• PRICEUS contains the price of the CD in US.
• PRICEUK contains the price of the CD in UK.
• TRACK contains information about a track of the
  CD.

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Document body

• If an .xml document has no
• style information, the browser
• will show the tree structure of
• the text.
• That means that the browser
• is aware of the structure
• implied by the tags.

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Document body

• If a tree can not be constructed by the browser,
  an error message will
• appear.
• Exercise Remove a closing tag from a valid XML
  document and open
• the file with a browser.

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Document body

• The document body may also contains CDATA

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Document body

• The document body may also contain references to
  special characters,
• such as the symbol

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Overview

• Introduction to XML
• XML documents
• CSS for XML

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CSS for XML

• To create a style sheet, use the following
  syntax
• selector attribute1value1 attribute2value2
  
• Selector is an element (or set of elements) from
  the XML document.
• Attribute and value are the style attributes and
  attribute values to be
• applied.
• Example
• ARTIST colorred font-weightbold
• will display the text of the ARTIST element in a
  red boldface type.

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CSS file

• Example The cascading style sheet JW.css

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CSS for XML

• The style sheet should be linked to the XML
  document. The syntax is
• lt?xml-stylesheet typestyle hrefsheet ?gt
• Style is the type of style sheet to access, and
  sheet is the name and
• location of the style sheet.

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Linking CSS to XML

• Example Link the XML document to a style sheet

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Formatted XML file

• The formatted XML file would look like

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Resources

• Download the student resources of the Patrick
  Careys book
• New Perspectives on XML
• http//www.course.com/studentcenter/downloads.cfm?
  isbn9780619101886CFID1593130CFTOKEN97788713