[Description] required and optional pseudo classes [Link To Spec] F.1 [Normative for XForms Basic] false [Normative for XForms Full] false [Test Case] 
F.1.b
F . 1 . a
F . 1 . b
F . 1 . c
F . 1 . d
F . 1 . e
F . 2 . a
F . 2 . b
F . 2 . c
F . 2 . d