Empty semantics:
annotation: annotation
annotation-xml: annotation-xml
presentation MathML (no annotations): presentation MathML
content MathML (no annotations): content MathML
presentation MathML ; annotation: presentation MathMLannotation
presentation MathML ; annotation-xml: presentation MathMLannotation-xml
content MathML ; annotation: content MathMLannotation
content MathML ; annotation-xml: content MathMLannotation-xml