XML : DTDs, XML Schemas
- Two methods to codify syntax rules of vocabulary used to describe document type
- what markup is allowed
- structural constraints on use of markup
- say nothing about what markup means
- Document Type Definition (DTD)
- inherited from SGML
- part of XML Recommendation
- XML Schema
- recent recommendation of W3C
- support for data-typing i.e. tighter control on element content
- support for combining vocabularies
- use XML syntax