Well-formed and Valid XML Documents

1
Well-formed and Valid XML Documents

• Kanda Runapongsa
• (krunapon_at_kku.ac.th)
• Dept. of Computer Engineering
• Khon Kaen University

2
Well-formed Valid

• Well-formed XML documents are the XML documents
  that obey XML syntax
• Valid XML documents are the XML documents that
  follow the rules of the schema of XML documents
• Well-formed XML documents do not need to be valid

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Well-formed XML Documents

• Must have XML Declaration
• Must have the root element
• Elements must have a closing tag
• Elements must be properly nested
• Element name of the end-tag must match with that
  of the start-tag

4
Well-formed XML Documents (Cont.)

• Attribute values must always be quoted
• Element and attribute names cannot be started
  with xml (for both uppercase and lowercase)
• Special characters (lt and ) cannot be used in
  text as they are used in markup

5
Some Rules for Checking Valid

• The value of attribute of ID type must be unique
  between all values of all ID attributes
• The value of IDREF attribute must match the value
  of some ID attribute in the document
• The value of IDREFS attribute can contain several
  references to elements with ID attribute
  separated with whitespaces.

6
Examples

• DTD
• lt!ELEMENT AAA (PCDATA)gt
• lt!ATTLIST AAA id ID REQUIREDgt
• lt!ELEMENT BBB (PCDATA)gt
• lt!ATTLIST BBB ref IDREF REQUIREDgt
• XML
• ltAAA id1gtHellolt/AAAgt
• ltBBB ref1gtHilt/BBBgt