(* Copyright (C) 2000, HELM Team.
 * 
 * This file is part of HELM, an Hypertextual, Electronic
 * Library of Mathematics, developed at the Computer Science
 * Department, University of Bologna, Italy.
 * 
 * HELM is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * HELM is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HELM; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA  02111-1307, USA.
 * 
 * For details, see the HELM World-Wide-Web page,
 * http://www.cs.unibo.it/helm/.
 *)

(******************************************************************************)
(*                                                                            *)
(*                               PROJECT HELM                                 *)
(*                                                                            *)
(*                     Ferruccio Guidi <fguidi@cs.unibo.it>                   *)
(*                     Irene Schena  <schena@cs.unibo.it>                     *)
(*                                 10/09/2002                                 *)
(*                                                                            *)
(*                                                                            *)
(******************************************************************************)


(* input data structures ****************************************************)

type svar = string (* the name of a variable for a resource set *)

type rvar = string (* the name of a variable for a resource *)

type vvar = string (* the name of a variable for an attribute value *)

type refine_op = ExactOp
               | SubOp
	       | SuperOp

type path = string list

type vvar_list = vvar list

type set_exp = SVar of svar
	     | RVar of rvar
             | Ref of val_exp
             | Pattern of val_exp
	     | Relation of bool * refine_op * path * set_exp * vvar_list
             | Select of rvar * set_exp * boole_exp
	     | Union of set_exp * set_exp
	     | Intersect of set_exp * set_exp
	     | Diff of set_exp * set_exp
	     | LetSVar of svar * set_exp * set_exp
	     | LetVVar of vvar * val_exp * set_exp
	     
and boole_exp = False
              | True
	      | Not of boole_exp
	      | Ex of rvar list * boole_exp   
	      | And of boole_exp * boole_exp
	      | Or of boole_exp * boole_exp
	      | Sub of val_exp * val_exp
	      | Meet of val_exp * val_exp
	      | Eq of val_exp * val_exp
	       
and val_exp = Const of string list 
            | RefOf of set_exp 
	    | Record of rvar * vvar
	    | VVar of vvar
	    | Attribute of bool * refine_op * path * val_exp
	    | Fun of string * val_exp

type query = set_exp


(* output data structures ***************************************************)

type value           = string list            (* the value of an attribute *)

type attribute       = string * value         (* an attribute *)

type attribute_group = attribute list         (* a group of attributes *)

type attribute_set   = attribute_group list   (* the attributes of an URI *)

type resource        = string * attribute_set (* an attributed URI *)

type resource_set    = resource list          (* the query result *)

type result = resource_set