Unit 2: Introduction to XML and DTD

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Unit 2 Introduction to XML and DTD
Instructor This unit is a review of XML and DTD.
Depending on the XML expertise of this class you
can skip or cover in detail. Encourage the
students to use it as reference material.

• Building J2EE Applications in SilverStream

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Section Objectives

• Introduction to XML
• Introduction to DTD

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What is XML?

• XML is a markup language that describes how data
  should be represented in a data file or I/O
  stream
• Tags identify each element within the document
• Self-describing
• Works with other technologies to
• Process data
• Display data

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What can XML be used for?

• Separate data from presentation
• Dont store data in HTML
• Exchange data between incompatible systems
• B2BTransactions
• Store data
• Instead of using text files
• Preference files

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J2EE and XML

• XML is used by assemblers to describe the
  components
• XML is used by deployers to specify the
  environment specific parameters
• You can use an XML parser to integrate XML into
  your applications
• SilverStream ships with the Xerces parser from
  the Apache Group

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XML Documents

• Header
• XMLDeclares the document is an XML document and
  the version of XML that the document is using.
• Document TypeDocument follows rules defined in a
  document type definition file (optional).
• Body
• XML tags to describe the data

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Introducing XML
Instructor This slide and the next slide should
be discussed together. You may need to flip back
and forth between the two.
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Introducing XML
Instructor This slide and the previous slide
should be discussed together. You may need to
flip back and forth between the two.
XML in IE5 browser
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Structure of XML Document
Root 0
A child has only ONE parent Child 0.1.2 for
example has parent 0.1
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Structure of XML Document
Book
Chapter
Section
Chapter Heading
Paragraph
Section Heading
Entries
Text
Figure
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XML Elements

• Opening tag
• Content
• Closing tag
• Empty Element
• XML is Case Sensitive!

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XML Attributes

• Element can have 0 or more
• Values must be in quotes
• Associate data with element

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Well Formed XML

• There must be a single root element
• All elements must be properly nested
• Element tags must match (lttaggtlt/taggt)
• Empty element may have a single tag definition
  (lttag/gt)
• Valid names start with alphabetic or a _
  (underscore) followed by any combination of
  letters, digits, hyphens, full stops or colons.
  Colons have a special meaning in allowing a name
  to be made unique through namespaces
• There must be no white space characters (space,
  tab or new line characters)
• The content between tags must not contain
  explicitly the following characters lt gt

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Other XML Elements and References

• CDATA
• Processing Instructions
• Comments

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Other XML Elements and References

• XML Declaration
• Version
• External DTD
• Character encoding

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Other XML Elements and References

• Entities
• Character References
• Elements or Attributes
• White space

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XML Declaration

• Remember the XML declaration
• Alerts whoever is processing the file that it
  contains XML data

lt?xml version1.0?gt
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Section Objectives

• Introduction to XML
• Introduction to DTD

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XML Document Types

• Well Formed XML Documents
• Document conforms to the rules discussed
  previously
• Valid XML Documents
• Well Formed document that follow rules defined
  in a Document Type Definition (DTD)

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Introduction to DTD

• Structured Declarations
• Well formed XML prior discussion
• Valid XML current discussion
• Do not conform to XML syntax
• Knowing the DTD allows you to create valid XML
  documents

The main purpose of this section is to teach the
student how to read and understand a DTD not to
write their own. So the topic should not be
covered in depth and the student should be
instructed to use it as a reference.
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Advantages of DTD

• Obeys DTD it is valid and well formed
• Specification known by developer
• Reliable Communication between applications
• Specify default values

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XML Document Structure
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The Basic Declaration
lt!DOCTYPE root_name . declarations of
elements, attributes and entities . gt
lt!DOCTYPE root_name SYSTEM locationgt
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The Basic Declaration
lt!DOCTYPE rootname lt!ELEMENT rootname
gt lt!ELEMENT gt lt!ELEMENT gt lt!ATTLIST
gt lt!ATTLIST gt lt!ATTLIST gt lt!ENTITY
gt lt!ENTITY gt lt!NOTATION gt lt!NOTATION
gt etc. etc. gt
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Declaring Elements

• Syntax
• Sequence
• Selection

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Declaring Elements

• Optional
• Iteration

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Content Definitions

• Elements
• PCDATA
• EMPTY
• ANY

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Entities and Entity Declarations

• Standard Entities
• General Entities
• Character Entities
• Escaping Characters
• Parameter Entities

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Defining Attributes
lt!ATTLIST element_name attribute_name
attribute type default values/requirements gt
ltbook price "12.45" currency "GBP"gtlt/bookgt
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Attribute Requirements

• REQUIRED
• FIXED
• IMPLIED

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Attribute Types

• CDATA
• Enumerated Types
• ID and IDREF

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Attribute Types

• NMTOKEN
• lt!ATTLIST book date_in NMTOKEN IMPLIEDgt
•  
• ltbook date_in "12-09-1999"gtlt/bookgt
• lt!ATTLIST book owners NMTOKENS REQUIREDgt
•  
• ltbook owners "Shakespeare Bacon"gtlt/book

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Attribute Types

• ENTITY
• lt!ENTITY fig5.jpg SYSTEM "E\XML Course\fig
  5.0.jpg" NDATA jpggt
• ltfigure image "fig5.jpg"/gt
• lt!ELEMENT figure EMPTYgt
• lt!ATTLIST figure image ENTITY REQUIREDgt
• lt!ENTITY fig5.jpg SYSTEM "E\XML Course\fig
  5.0.jpg" NDATA jpggt

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Attribute Types

• NOTATION
• lt!NOTATION jpg SYSTEM "D\Program
  Files\Plus!\MicrosoftInternet\iexplore.exe"gt

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Normalisation and White Space

• Quotes Stripped
• Entities Replaced
• xmlspace

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Sample DTD
lt!ELEMENT poem-collection (poem)gt lt!ELEMENT
poem(author,description?,references,
line,(date-createddate-received))gt lt!ATTLIST
poem type computergt lt!ATTLIST poem subtype
not applicablegt
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DTDs and J2EE

• All J2EE implementations create deployment
  descriptors based on DTDs created by Sun
  Microsystems.
• SilverStream has created DTDs for deployment
  plans, as well as some options for its
  command-line utilities.

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Demo of J2EE DTD and XML
Instructor Use the Web Application DTD file
in SILVERSTREAM_HOME\Resources\DTDCatalog\web-a
pp_2_2.dtd And the SilverBooks web.xml file in
SILVERSTREAM_HOME \samples\SilverBooks\src\silv
erbooks\docroot\web-inf\web.xml Have the students
open the files in a text editor or even using IE
and discuss how the DTD requirements define what
must appear in the XML file.

• Review of the Web Application DTD and web.xml for
  SilverBooks