;;; -*- Mode: Lisp; Package: STELLA; Syntax: COMMON-LISP; Base: 10 -*-

;;; File implementing a part-of set of relations based on the
;;; the RCC5 (Region Connection Calculus)
;;; Author: University of Southern California
;;; Version: $Id: partof.plm 2434 2011-06-07 16:08:02Z tom $

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; Version: MPL 1.1/GPL 2.0/LGPL 2.1                                          ;
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; The Original Code is the PowerLoom KR&R System.                            ;
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; The Initial Developer of the Original Code is                              ;
; UNIVERSITY OF SOUTHERN CALIFORNIA, INFORMATION SCIENCES INSTITUTE          ;
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;;;;
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(in-module "PL-KERNEL-KB")

(defmodule "PART"
  :documentation "Module for a part-of relations based on Region Connection Calculus 5 (RCC5) relations.  $Revision: 2434 $

This implementation is an efficient encoding of the part-of relations.
Inference is limited to transitive relationships in the part-of hierarchy
and certain disjointness axioms.

Implements DISCRETE (DR), OVERLAPS (PO), PROPER-PART-OF (PPI)
relations directly. For EQ the standard PowerLoom equality (=) is
used.  That means that if equality is desired, one must create the
regions using the REGION function, so that they end up being skolems.

Also, there is a basic DIRECT-PART-OF relation for expressing a
relationship where there is no intervening parts.  This is much more
efficient than trying to derive that relationship using a negated
existential.

Examples:
 (assert (discrete (region g0) (region g1)))
 (assert (proper-part-of (region g1) (region g2)))
 (assert (proper-part-of (region g2) (region g3)))
 (assert (= (region g3) (region g3alt)))

 (retrieve all (proper-part-of (region ?x) (region ?y)))
 (retrieve all (discrete (region ?x) (region ?y)))
 (retrieve all (not (discrete (region ?x) (region ?y))))

For more background on the RCC5, consult
  David A. Randell and Zhan Cui and Anthony Cohn,
  'A Spatial Logic Based on Regions and Connection',
  KR '92. Principles of Knowledge Representation and Reasoning:
          Proceedings of the Third International Conference,
  pp. 165-176, 1992.

  Anthony G. Cohn, Brandon Bennett, John Gooday and Nicholas M. Gotts,
  'Representing and Reasoning with Qualitative Spatial Relations About Regions',
  in Spatial and Temporal Reasoning, Oliviero Stock (ed).,
  (Kluwer Academic Publishers: Boston), 1997.
"
  :includes ()
  :uses ())

(defconcept /part/geometric-region)
(defconcept /part/geometric-region-2d (/part/geometric-region))
(defconcept /part/geometric-region-3d (/part/geometric-region))
(deffunction /part/region ((?x THING)) :-> (?g /part/GEOMETRIC-REGION))

(defrelation /part/discrete ((?x /part/geometric-region) (?y /part/geometric-region))
  :documentation "DISCRETE: Discrete regions with no overlap or part containment."
  :=>> (/part/discrete ?y ?x)		; Symmetry, forward-chained
  )

(defrelation /part/overlaps ((?x /part/geometric-region) (?y /part/geometric-region))
  :documentation "OVERLAPS: Partially Overlaps regions"
  :=>> (/part/overlaps ?y ?x)
  )

(defrelation /part/proper-part-of ((?x /part/geometric-region) (?y /part/geometric-region))
  :documentation "PROPER-PART-OF: Proper Part Inverse.  ?x is the proper part of ?y"
  ;; NOTE: Use the assertion level query as part of the axiom to improve
  ;;       efficiency of the query.
  :<= (exists (?z) (and (query (/part/proper-part-of ?x ?z) :how-many :all :inference-level :assertion)
			(bound-variables ?x ?z)
			(/part/proper-part-of ?z ?y)))
  )