Element Types Must Be Declared

The first basic ingredient in validity is that all the elements that appear in the document must have been declared in the DTD.

This seems obvious but actually it is becoming controversial; a lot of people would like to be able to do "partial validation" of documents, just checking that the elements that have been declared are valid. There's no way to do this in XML as it stands now.

Back-link to spec

Copyright © 1998, Tim Bray. All rights reserved.