Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

We now have three partially ordered steps in our plan with one initial and one
goal condition. These five partially ordered plans are presented below in a
column structure.
Plan 1: If Clear ( C) ∧ Clear (B) ∧ On (B, Table)
Add: On (C,B)
Delete: Clear (B)
Plan 2: If Clear (A) ∧ Clear (B) ∧ On (B, Table)
Add: On (B,A)
Delete: Clear (A)
Plan 3: If On (A,B) ∧ Clear (A)
Add: On (A, Table) ∧ Clear (B)
Delete: On (A,B)
Plan 4: If Nil
Add: On (A,B) ∧ Clear (C ) ∧ Clear (A)∧ On (C, Table) ∧
On (B, Table)
Delete: Nil
Plan 5: If On (B,A) ∧ On (C,B)
(goal) Add: Nil
Delete: Nil
The complete order of the plans that maintain satisfiability of the preconditions
of each partial plan is given by
plan 4 < plan 3 < plan 2 < plan 1 < plan 5
where plan j < plan k means plan j is to be executed prior to plan k.
In the above scheme for ordering a list of partially ordered plans, we
demonstrated only two steps: addition of steps and promotion by adding
constraints.
Let us now illustrate the principle of declobbering. Suppose, we choose
the totally ordered plan as follows:
plan 4 < plan 3 < plan 1 < plan j < plan 2 < plan 5