XPath = List(Exp1).
Exp1 : Disjunction | Child | Descendant | Filter | ElementTest | Wildcard.
Disjunction = "|" <args> NList(Exp1).
Child = "/" <args> NList(Exp1).
Descendant = "//" <args> NList(Exp1).
Filter = "[" Restriction "]" Exp1.
Restriction = And(Absolute).
Absolute : AbsChild | AbsDescendant.
AbsChild = "/" Exp1.
AbsDescendant = "//" Exp1.


Main = <s> String.