% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % %
%                                                                           %
% File:            dfsa4b.dtr                                               %
% Purpose:         DFSA solving wolf/goat/cabbage problem                   %
%                  (straightforward version of the automaton)               %
% Author:          Geoffrey K. Pullum, 12 October 1994                      %
% Email:           gkp@ling.ucsc.edu                                        %
% Address:         Stevenson College, UCSC, Santa Cruz, CA 95064, USA       %
% Related files:   dfsa4a.dtr                                               %
% Documentation:   see reference given in dfsa4a.dtr                        %
%                                                                           %
%        Copyright (c) UC Santa Cruz 1994.  All rights reserved.            %
%                                                                           %
% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % %


% The problem the automaton solves is how a man can get a wolf, a goat, and
% a box of cabbages safely across a river in a tiny boat that can hold the
% man together with just one of the three items.  Note that because of
% natural food preferences, the wolf cannot be left alone on either bank
% with the goat, and the goat must never be left alone with the cabbages
% (though the wolf can be safely left with the cabbages).

% This is a variation on the straightforward approach in dfsa4a.dtr that is
% intended to illustrate more of DATR's inheritance capabilities -- but one
% of the things it illustrates is that things can be harder to follow when
% efficient use is made of inheritance and higher nodes.  The nodes named
% Node1 to Node 6 are simply grouping nodes, whose only point is to simplify
% the description.  The other nodes correspond to the states of the automaton
% in dfsa4a.dtr (e.g. Lmg_wcR is the state where the man and the goat are on
% the left bank and the wolf and the cabbages are on the right); but these
% are now more compactly stated in many cases.  However, the actual number
% of equations eliminated is quite small because of the small number of
% attributes per node in this example, so crude size comparisons between
% dfsa4a.dtr and dfsa4b.dtr are not very instructive.

Solution:
    <> == Lmwgc_R.

Node1:
    <mc> == impossible move
    <> == task incomplete.

Node2:
    <> == Node1
    <m> == double disaster
    <mw> == goat eats cabbages
    <mc> == wolf eats goat.

Node3:
    <> == Node1
    <mw> == Node1:<mc>.

Node4:
    <> == Node1
    <mg> == Node1:<mc>.

Node5:
    <> == Node3
    <m> == Node2:<mw>.

Node6:
    <> == Node1
    <m> == Node2:<mc>.

Lmwgc_R:
    <> == Node2
    <mg> == Lwc_mgR:<>.

Lwc_mgR:
    <> == Node3
    <m> == Lmwc_gR:<>
    <mg> == Lmwgc_R:<>.

Lmwc_gR:
    <> == Node4
    <m> == Lwc_mgR:<>
    <mw> == Lc_mwgR:<>
    <mc> == Lw_mgcR:<>.

Lc_mwgR:
    <> == Node6
    <mw> == Lmwc_gR:<>
    <mg> == Lmgc_wR:<>.

Lw_mgcR:
    <> == Node5
    <mc> == Lmwc_gR:<>
    <mg> == Lmwg_cR:<>.

Lmgc_wR:
    <> == Node5
    <mg> == Lc_mwgR:<>
    <mc> == Lg_mwcR:<>.

Lmwg_cR:
    <> == Node6
    <mg> == Lw_mgcR:<>
    <mw> == Lg_mwcR:<>.

Lg_mwcR:
    <> == Node4
    <m> == Lmg_wcR:<>
    <mc> == Lmgc_wR:<>
    <mw> == Lmwg_cR:<>.

Lmg_wcR:
    <> == Node3
    <m> == Lg_mwcR:<>
    <mg> == L_mwgcR:<>.

L_mwgcR:
    <> == succeeded
    <m> == Node2
    <mw> == Node2
    <mc> == Node2
    <mg> == Lmg_wcR:<>.

% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % %

% Some example theorems:
% 
% Solution:
%   <mw> = goat eats cabbages
%   <mc m> = wolf eats goat
%   <mc m mw> = wolf eats goat
%   <mg m mc m mw> = goat eats cabbages
%   <mg m mc mg mw m> = task incomplete
%   <mg m mc mg mw m mg> = succeeded
%   <mg m mc mg mw m mg mg> = task incomplete
%   <mg m mc mg mw m mg mg mg> = succeeded
%   <mg m mc mg mw mc mg mw mc mc mw m mc> = wolf eats goat
%   <mg m mc mg mw mc mg mw mc mg mw m mg> = succeeded.

% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % %

# hide 
    Node1 Node2 Node3 Node4 Node5 Node6 Lmwgc_R Lwc_mgR Lmwc_gR
    Lc_mwgR Lw_mgcR Lmgc_wR Lmwg_cR Lg_mwcR Lmg_wcR L_mwgcR.

# show   
    <mw>
    <mc m>
    <mc m mw>
    <mg m mc m mw>
    <mg m mc mg mw m>
    <mg m mc mg mw m mg>
    <mg m mc mg mw m mg mg>
    <mg m mc mg mw m mg mg mg>
    <mg m mc mg mw mc mg mw mc mc mw m mc>
    <mg m mc mg mw mc mg mw mc mg mw m mg>.

% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % %

% The next line is the Revision Control System Archive Id: do not delete it.
% $Id: archive.dtr,v 1.1 1997/04/09 20:40:33 root Exp $