unification:
  AND:
    unify_redundant_feature:
      case1:
        expr1: "+X & +Y"
        expr2: "+X"
        result: "+X & +Y"
      case2:
        expr1: "+X & +Y"
        expr2: "+Y"
        result: "+X & +Y"
sentence:
  case1:
    provide: "^X"
    request: "+X"
    result: true
  case2:
    provide: "^X"
    request: "*"
    result: true
  case3:
    provide: "^X"
    request: "+Y"
    result: false
  case4:
    provide: "^X"
    request: "-X"
    result: false