XML : DTDs, XML Schemas
- Means to codify syntax rules of vocabulary
- what markup is allowed
- structural constraints on use of markup
- N.B. say nothing about what markup means
- Document Type Definition
- part of XML Recommendation
- W3C XML Schema
- recent W3C recommendation
- data-typing i.e. tighter control on element content
- support for combining vocabularies
- uses XML syntax
- Parser/authoring tool can validate markup of instance against rules in DTD or Schema