sample-blocks-domain.pl

   1 % -------------------- Sample of a planning domain --------------------
   2
   3
   4 % the following line specifies which predicates or fluents are defined
   5 % across two or more files. These predicates appear here, and in the
   6 % initial state and goal definitions, in sample-blocks.pl
   7
   8 :- multifile on/3, clear/2.             % <name>/<number of parameters>
   9
  10
  11
  12
  13 % -- Primitive control actions: this section defines the name and
  14 % the number of parameters of the actions available to the planner
  15
  16 primitive_action( move(_,_) ).  % underscore means `anything'
  17
  18
  19
  20
  21 % -- Preconditions for primitive actions: describe when an action
  22 % can be carried out, in a generic situation S
  23
  24 poss( move(What, Where), S ) :-         % implication poss() <= precond
  25   clear(What, S),
  26   clear(Where, S),
  27   not(heavy(What)),                     % can't move the table (or other heavy obj)
  28   not(What = Where),            % can't move a block on top of itself
  29   not(on(What, Where, S)).      % can't move around the same support
  30                                                         % (applies for the table)
  31
  32
  33
  34 % -- Successor State Axioms for primitive fluents: describe the value
  35 % of fluent based on the previous situation and the action chosen for
  36 % the plan.
  37
  38 % The general form of a successor state axiom is:
  39 %
  40 % a fluent is true in the situation resulting from applying action A
  41 % in situation S, if
  42 %   - action A makes the fluent true; OR
  43 %   - the fluent was already true in the previous situation S,
  44 %       AND action A will not change this fact, by making it false.
  45
  46
  47 on(Block, Support, result(A, S)) :-
  48   A = move(Block, Support);
  49   on(Block, Support, S), not(A = move(Block, _)).
  50
  51
  52 clear(table, _).        % special case, the table is clear any situation
  53                                         % (i.e. there is always space on the table)
  54
  55 clear(Block, result(A, S)) :-
  56   A = move(Something, _), on(Something, Block, S);
  57   not(A = move(_, Block)), clear(Block, S).
  58
  59
  60 % ---------------------------------------------------------------------
  61 % ---------------------------------------------------------------------