XML EXtensible Markup Language

1
XMLEXtensible Markup Language

• XML is designed to describe data and to focus on
  what data is. HTML is designed to display data
  and to focus on how data looks.
• XML is created to structure, store, and to send
  information
• XML tags are not predefined. You must define your
  own tags
• XML uses a DTD or an XML Schema to describe the
  data

2
XML an example

• XML was created to structure, store, and to send
  information
• An Example
• ltnote date10/30/2007gt
• lttogtChucklt/togt
• ltfromgtJudylt/fromgt
• ltheadinggtReminderlt/headinggt
• ltbodygtDont forget me this weekend!lt/bodygt
• lt/notegt
• The above is just pure information wrapped in XML
  tags. Someone must write a piece of software to
  send, receive or display it.

3
How can XML be Used?

• XML can separate data from HTML
• With XML, data is stored in separate XML files
• XML is used to exchange data
• XML and B2B. With XML, financial information can
  be exchanged over the Internet
• XML can be used to share data
• XML can be used to store data
• XML can be used to create new languages
• All future applications will exchange their data
  in XML

4
XML Syntax Rules

• lt?xml version1.0 encodingISO-8859-1 ?gt
• ltnotegt
• lttogtChucklt/togt
• ltfromgtJudylt/fromgt
• ltheadinggtReminderlt/headinggt
• ltbodygtDont forget me this weekend!lt/bodygt
• lt/notegt
• The first line the XML declaration defines
  the XML version and the character encoding
• The next line describes the root element
• The next 4 lines describe 4 child elements of the
  root
• The last line defines the end of the root element

5
XML Syntax (continued)

• All XML elements must have a closing tag
• The XML declaration is not a part of the XML
  document. It is not an XML element, and it should
  not have a closing tag
• XML tags are case sensitive
• XML elements must be properly nested
• XML documents must have a root element
• XML attribute values must be quoted
• With XML, white space is preserved
• The syntax for writing comments in XML is similar
  to HTML
• lt!-- This is a XML comment --gt

6

• XML (EXtensible Markup Language)
• Introduction to XML
• What is HTML
• What is XML
• XML Syntax
• Elements must have a closing tag
• Elements must be properly nested

ltbookgt lttitlegtXML (Extensible Markup
Languagelt/titlegt ltprod id"33-657"
media"paper"gtlt/prodgt ltchaptergtIntroduction to
XML ltparagtWhat is HTMLlt/paragt ltparagtWhat is
XMLlt/paragt lt/chaptergt ltchaptergtXML Syntax
ltparagtElements must have a closing
taglt/paragt ltparagtElements must be properly
nestedlt/paragt lt/chaptergt lt/bookgt
7
XML Elements

• XML elements are related as parents and children
• An XML element can have element content, mixed
  content, simple content, or empty content
• An element can have attributes
• XML documents often have a corresponding
  database, in which fields exist corresponding to
  elements in the XML document. A good practice is
  to use the naming rules of your database for the
  elements in the XML documents

8
XML Attributes

• Attributes are used to provide additional
  information, which is not relevant to the data,
  about elements
• Try to avoid using attributes.

ltnotegt ltdategt ltdaygt10lt/daygt
ltmonthgt30lt/monthgt ltyeargt2007lt/yeargt lttogtC
hucklt/togt ltfromgtJudylt/fromgt ltheadinggtReminderlt/hea
dinggt ltbodygtDont forget me this
weekend!lt/bodygt lt/notegt
ltnote date10/30/2007gt lttogtChucklt/togt ltfromgtJudy
lt/fromgt ltheadinggtReminderlt/headinggt ltbodygtDont
forget me this weekend!lt/bodygt lt/notegt
9
XML Validation

• XML with correct syntax is Well Formed XML
• XML validated against a DTD is Valid XML
• A valid XML document is a Well Formed XML
  document, which also conforms to the rules of a
  DTD
• XML DTD
• A DTD defines the legal elements of an XML
  document
• A DTD is used to define the document structure
  with a list of legal elements
• XML Schema
• An XML based alternative to DTD

10
Displaying XML Files

• WITH CSS

• WITH XSL

• Examples

• XSL (eXtensible Stylesheet Language) is far more
  sophisticated than CSS
• Examples

11
XML Namespaces

• The XML namespace attribute is placed in the
  start tag of an element and has the following
  syntax. The syntax is
• xmlnsnamespace-prefix"namespaceURI
• where namespaceURI provides the namespace a
  unique name

lthtable xmlnsh"http//www.w3.org/TR/html4/"gt lt
htrgt lthtdgtAppleslt/htdgtlthtdgtBananaslt/htdgt lt/
htrgt lt/htablegt
ltftable xmlnsf"http//www.w3schools.com/furnitu
re"gt ltfnamegtAfrican Coffee Tablelt/fnamegt ltfwi
dthgt80lt/fwidthgt ltflengthgt120lt/flengthgt lt/ftab
legt
12
XML CDATA

• Text inside a CDATA section will be ignored by
  the parser
• A CDATA section starts with lt!CDATA and ends
  with gt

ltscriptgt lt!CDATA function matchwo(a,b) if
(a lt b a lt 0) then return 1 else
return 0 gt lt/scriptgt
13
XML Encoding

• To let your XML parser understand foreign
  characters, you should save your XML documents as
  Unicode
• Windows 2000 Notepad can save files as Unicode
  using UTF-16 encoding
• You will get error message
• if your file was save as Unicode/UTF-16 but the
  encoding attribute specified a single-byte
  encoding like Windows-1252, ISO-8859-1 or UTF-8
• If your document was saved with single-byte
  encoding, but the encoding attribute specified a
  double-byte encoding like UTF-16

14
XML Editors

• XML Editors will help you to write error-free XML
  documents, validate your XML against a DTD or a
  schema, and force you to stick to a valid XML
  structure.
• XML Schema to define XML structures and data
  types
• XSLT to transform XML data
• SOAP to exchange XML data between applications
• WSDL to describe web services
• RDF to describe web resources
• XPath and XQuery to access XML data
• SMIL to define graphics
• Example Altova XMLSpy