The best replacement for dtd is schema.

The best alternatives to dtd are rated as following:
★★★★★  schema
★★★★  xsd
★★★  xml schema
★★  schema xml
★★  wsdl
★★  xsd difference
★  xsd schema
★  namespace
★  relax ng
  xsl
  strict.dtd
  schemas

Your alternative for dtd is not listed? Suggest!
Speaking about dtd, one probably shouldn't forget about xml.

Other search terms related to dtd and their ratings are:
★★★★★ xml
★★★ xml example
★★★ xml examples
doctype
You have in mind a companion for dtd and it is not yet here? Propose!



Google Trends

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dtd
schema
xsd