slide 20

Why DTD Not Schemas? — Technical

• Which schema?: W3C XML Schema, RELAX NG, Schematron, XDR, ...
• Modularity
  • Easy extension for new content or functional modules
  • Table models: CALS and XHTML, other
• Preserving intellectual content (e.g., MathML which was not yet in schema)
• Schema strength: data types and data typing
  • very little in journals that can use types, even in the metadata
  • content models are highly diverse and not derivable
  • goal was “preservation” not “enforcement” and checking
• Many sets of character entities would need to be included in a DTD anyway