6.1 Well Formed and Valid Documents

• A XML document must be well formed
  • Every start element <...> must have a corresponding end element </...>
  • Elements must be properly nested.
  • A document must have a single root
  • Attributes must be delimited by single (') or double (") quotes
  • An empty element may use a shortened notation <.../>
  • Element and attribute names are case sensitive
• A DTD defines a XML markup language: a vocabulary of element and attribute names, and constraints on how they may be used
• A document obeying a DTD is said to be valid
• A DTD is consisted of deflations:
  <!KEYWORD name parameters>