sig
  val is_simple_conjunct : Logical_algebra_types.logical_algop_expr -> bool
  val extract_pred_desc :
    Logical_algebra_types.logical_algop_expr ->
    Xquery_algebra_ast.predicate_desc
  val construct_singleton_select :
    Logical_algebra_types.logical_algop_expr ->
    Logical_algebra_types.logical_algop_expr ->
    Xquery_ast.expr_handle ->
    Finfo.finfo -> Logical_algebra_types.logical_algop_expr
  val conjunctive_merge_select :
    Logical_algebra_types.logical_algop_expr ->
    Logical_algebra_types.logical_algop_expr ->
    Logical_algebra_types.logical_algop_expr
  val remove_conjunct :
    Logical_algebra_types.logical_algop_expr ->
    int -> Logical_algebra_types.logical_algop_expr option
end