ResultSet
result variable: x
result variable: y
result variable: a
size: 2
solution: ResultSolution
  binding: ResultBinding
    variable: x
    value: r2
  binding: ResultBinding
    variable: y
    value: r1
  binding: ResultBinding
    variable: a
    value: r2
solution: ResultSolution
  binding: ResultBinding
    variable: x
    value: r1
  binding: ResultBinding
    variable: y
    value: r2
  binding: ResultBinding
    variable: a
    value: r1