Planning problems can be acquired by loading a sample problem or defining a new problem in "Create" mode. To load a sample problem, click "Load Sample Problem" from the "File" menu. Then select a problem from the drop-down list and click "Load."
To create a new planning problem, select "Create New Problem" from the "File" menu.
When creating a problem, the first step is to define the initial state. This is the starting positions of all the blocks in the problem. Be sure that you are in "Create Initial State" mode, as indicated by the button above the initial state panel at the bottom of the screen.
You can now create blocks by selecting "Create New Block" on the button panel and then clicking the position on the table where the new block is to appear. A block properties window will then open. You can click the "Ok" button to proceed or change the block's name and/or colour before clicking "Ok." Clicking again on the canvas will create another block.
Use the modes on the button panel to delete blocks and change the block's properties (name and colour). Note that blocks can be rearranged by dragging them to new positions on the table or onto other blocks. As blocks are created or rearranged, the Prolog-style text representation of the initial state is displayed and updated in the Initial State box below the table.
Once the initial state has been created, the goals for the planner to achieve must be specified. Goals can be specified visually by rearranging the initial state, or the goals can be specified by manually choosing goal atoms and terms.
Creating Goals Visually After creating the initial state, select the "Create Goal State" button the right-side above the goal state panel. When asked to select a goal entry method, select the first option, "Specify goal state by graphically rearranging the initial state." You can now move blocks around to create the goal state. Notice how the goals display in the lower right corner changes as you move the blocks.
If desired, you can click the "Reorder Goals" button to change the order of the goals to be achieved.
Creating Goals by Specifying Goal Atoms and Terms If you need more control over the goals, they can be entered individually instead of graphically. In this case, select the "Create Goal State" button the right-side above the goal state panel and when asked to select a goal entry method, select the second option, "Specify Goals by Entering Atoms." There will now be two new buttons available at on the button panel, "Add New Goal" and "RemoveGoals" Clicking "Add New Goal" opens a window that allows you to create a goal atom by selecting a predicate and then selecting terms for the predicate. If necessary, buttons to access the goal removal and goal reordering features are available.
Once a goal entry method has been chosen, the program will default to that method whenever "Create Goal State" is selected. If you want to change goal entry method later, you may do so via the radio buttons at the bottom of the goal state panel.
When the initial state and goals of a planning problem have been created (or loaded), select the "Solve" tab. In this mode, a tree is created as a visual representation of how the STRIPS planner works.
Rectangular nodes represent actions oval nodes represent subgoals of the parent action. Red action nodes indicate that the action has not been added to the plan, and red goal nodes are goals that have not been achieved. Green action nodes have been added to the plan and green goal nodes have been achieved.
Initially, the tree consists of a root node labelled "Solved" and the initial goals are visualized as subgoals of the root action node, "Solved." Click the "Step" button to watch the algorithm attempt to find a plan by choosing actions to achieve all of the goals.
While the algorithm is running, it is helpful to open the Current State window (Click "View Current State"). This window visually displays the current position of all the blocks and also shows the text representation of the current state. You can also click "View Plan" to view actions that have been added to the plan at the current stage of the algorithm.
If the algorithm is able to find a plan, you may wish to view an animation of that plan by clicking the "Run Plan" button. This will open a window showing the initial state of the planning problem. You can then press the "Run Plan" button to begin the animation.
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