From Extensible Markup Language (XML) 1.1 ( 2004-02-04) An element type has element content when elements of that type MUST contain only child elements (no character data), optionally separated by white space (characters matching the nonterminal S).
From Extensible Markup Language (XML) 1.0 ( 2000-10-06) An element type has element content when elements of that type must contain only child elements (no character data), optionally separated by white space (characters matching the nonterminal S).