slide 16

Features of XML DTD

• Defined in the XML Specification
• About structure of elements
• Validation is
  • all or nothing
  • changes the information set (default attributes for example)
• Defined by regular grammar (in lay terms, a simple program can infer the relation of tokens by parsing a character stream sequentially)
• Elements
  • are declared with content models
  • data content is conceived of as strings
• Referential integrity between elements enforceable through attributes (ID / IDREF)

Anything else is considered “higher level” and pushed up to another layer