In DTD Land, the document is either valid or invalid.

There is no room for partial validity.

Everything must be declared.

Don't cross he dictator or you'll lose your content!

In the days of SGML, if it wasn't valid, you couldn't load your document.

Hence the label "Dictator".

...but Benevolent Dictator because the point of the DTD was well intentioned.

Lesson: Validity is only one state and invalid or non-validateable documents are OK.