XML Training Course

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XML Training Course

• Module 3 XML Validation with DTDs

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What to expect this Session

• Discussion of well-formed and valid XML
  Documents
• What is a DTD?
• Creating a DTD
• Controlling Elements
• Controlling Attributes
• Shortcomings of DTDs

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Well-formed vs. Valid

• Two ways to be right
• Well-formed all the syntax rules have been met
• Valid the document has been successfully
  validated against a defining DTD or XML Schema

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Document Structures

• Data must have rules
• Define what data types
• Define sizes
• Define order

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DTDs Defined

• Data Type Definitions
• Used to enforce structure requirements for and
  XML Document

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DTDs in Use

• Allowed Tags
• Allowed elements
• Allowed attributes
• of occurrences of each element
• Order in which elements may appear

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Declare a DTD

• XML document declares that it has an associated
  DTD by including the !DOCTYPE tag.
• lt!DOCTYPE root-element identifier-type
  identifiergt
• lt!DOCTYPE project_description SYSTEM
  "project.dtd"gt
• lt!DOCTYPE catalog SYSTEM "catalog.dtd"gt
• lt!DOCTYPE menu PUBLIC www.cafe.com/menu.dtdgt

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Create a DTD

• DTD consists of a list of statements, referred to
  as Content Models.
• These statements define the allowed and the order
  in which the should appear.
• General format of the statement looks like
• lt!ELEMENT elementname (elementtype modifiers)gt
• lt!ELEMENT Entree (Meat)gtA entrée can contain one
  and only one occurrence of meat.

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DTD Element Modifiers
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Example
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Example, cont
PCDATA Parsed Character Data
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DTD Attribute Declarations

• Use the lt!ATTLIST tag to define Attributes.
• General format looks like this
• lt!ATTLIST associatedelement
• attributename1 attributetype1 modifiers
• attributename2 attributetype2 modifiers
• ...
• attributenameN attributetypeN modifiersgt

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DTD Attribute Types
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DTD Attribute Modifiers
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Example, cont
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DTDs Shortcoming

• They can only validate structure of a document.
• They can not enforce any type of rules for a
  particular element.
• To enforce rules use and XML Schema

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Review this Session

• Discussion of well-formed and valid XML
  Documents
• What is a DTD?
• Creating a DTD
• Controlling Elements
• Controlling Attributes
• Shortcomings of DTDs

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Build an XML DTD