datatypes xs = "http://www.w3.org/2001/XMLSchema-datatypes"
element doc {
  (
    element p {
      (
        text |
        element em { text } |
        element a {
          (attribute name { text } |
          attribute href { xs:anyURI }),
          text
        }
      )*
    } |
    element h1 { text }
  )*
}