Introduction to XML

1
Introduction to XML

• eXtensible Markup Language the universal format
  for structured documents and data on the Web.
• A simplified subset of the Standard Generalized
  Markup Language (SGML).
• It enables the separation of the meaning or
  semantics of the data from the way it is used by
  an application or rendered on the screen or
  output device.
• XML is case-sensitive, the opening and closing
  tags both must be consistent.
• Spaces are not allowed in elements names

2
(No Transcript)
3
(No Transcript)
4
XML Tags

• XML allows us to create our own set of
  self-describing tags to identify our data.
• Start tags must have corresponding end tags. A
  pair of start and end tags is called an element.
  An empty tag is essentially a start and end tag
  in one, and is identified by a trailing slash
  after the tag name (e.g. ltBR/gt).
• XML is case-sensitive, the opening and closing
  tags both must be consistent.
• Spaces are not allowed in elements names

5
Declare an XML Document
lt?xml version"1.0" standalone"yes"
encoding"ISO-8859-1"?gt
6
Build an XML Document

• XML documents require a root element. The root
  element appears only once and encapsulates the
  entire XML elements and data in the document
• In a well-formed XML document, all start tags
  need to be properly closed.
• A well-formed XML structures your data in a
  relational hierarchical tree.
• All attribute values must be within single or
  double quotes.

7
An Example of XML Document
lt?xml version"1.0" standalone"yes"?gt ltlibrarygt
ltbook call_no"PZ3.S8195Gr6"gt ltcover
href"grapes.gif" alt"Grapes of Wrath"/gt
lttitlegtThe Grapes of Wrathlt/titlegt ltauthorgt
ltlast_namegtSteinbecklt/last_namegt
ltfirst_namegtJohnlt/first_namegt lt/authorgt
ltpublishergtViking Presslt/publishergt
ltpub_yeargt1939lt/pub_yeargt lt/bookgt lt/librarygt
8
(No Transcript)
9
View XML Document

• A well-formed XML document by itself simply
  provides a way to structure data.
• To set the rules that govern the valid ways those
  tags must be used, we can use a DTD, or a
  document type definition.
• XML can be viewed by incorporating HTML tags
  and/or along with style sheet.

10
Document Type Definition (DTD) File

• Define which elements are available, in what
  sequence they must appear, how often they may be
  used, the possible nesting structure of the
  elements, and the attributes they may contain as
  well.
• XML is really a formal specification language
  which processors use first to parse the DTD and
  then to read the document to identify where every
  element type comes and how each relates to the
  other.

11
XSL

• XSL is XML-based, so it has to adhere to the same
  XML rules for well-formedness.
• An XSL style sheet contains templates, each of
  which dictates rules and is specified with a
  matching pattern.
• When the XSL processor finds XML data that
  matches a template pattern, it extracts XML data,
  filters out unwanted sections, and manipulates
  the data into some presentable layout.

12
Use XSL with XML

• XSL style sheets are saved as files with an .xsl
  extension.
• We need to specify the style sheet in an XML
  document
• lt?xml-stylesheet type"text/xsl"
  href"library.xsl"?gt

13
An Example

• ltxsltemplate match"/Recipe"gt indicates that
  this template is to be applied when a ltRecipegt
  element is encountered at the input.
• ltxslvalue-of select"Name"/gt instructs the XSL
  processor to go get the text contained in the sub
  element ltNamegt.
• ltxslapply-templatesgt command, which tells the
  XSL processor to apply all the other templates in
  the file to the input.

14
Applications to Database

• Represent database schema as a set of DOM
  objects.
• Write the schema out as XML.
• Use XSL to format the XML as HTML and you've got
  a complete, browseable schema reference that's
  always up to date.