Part of the XML motivation was for something simpler than SGML. SGML has no opinions on rendering, since it's just a generic markup language. Nor does it have

Part of the XML motivation was for something simpler than SGML. SGML has no opinions on rendering, since it's just a generic markup language. Nor does it have opinions on "what do with a hr that's a direct descendant of the table despite not being permitted", to pick the first example from the spec (it should be treated as a preceding sibling).