Document(
  Prefix(ex <http://example.org/example#>)
  Prefix(func <http://www.w3.org/2007/rif-builtin-function#>)
  Prefix(pred <http://www.w3.org/2007/rif-builtin-predicate#>)
  Prefix(xs <http://www.w3.org/2001/XMLSchema#>)

  Group(
   Forall ?x ( 
     ex:root(?x) :-
       And (External(pred:is-literal-decimal(?x))
              External(func:numeric-subtract(External(func:numeric-multiply(?x External(func:numeric-multiply(?x ?x)))) ?x))
                  = "0"^^xs:decimal
       )
   )
  )
 )