Establishing Open Conditions

Figure 15 shows the procedure used. Procedure EstablishPre shows the methods of adding a new step and reusing an existing step; they are essentially the methods used in UCPOP extended to reflect the need to check and propagate contingency labels.

Procedure EstablishUnk shows methods of adding a new decision and reusing an existing decision that are specific to Cassandra. The issues involved were discussed in Section 4.2.

Establish(Plan, Open)

1. If the open condition is not of type :unknown do EstablishPre(Plan, Open) and return the resulting list of plans;
2. If the open condition is of type :unknown with source of uncertainty Uncertainty and outcome Outcome do EstablishUnk(Plan, Open, Uncertainty, Outcome) and return the resulting list of plans.

1. Initialize list NewPlans;
2. For each effect Eff resulting from a step Step in Plan
   If Eff can occur in every contingency in which Open must be established
   and if Eff can precede the step SupStep that Open is required to support
   and if there is a postcondition EffCond of Eff that can unify with condition Cond that Open is required to establish:
   • Complete the link Open by using Eff as the establishing effect;
   • Add the resulting partial plan to NewPlans;
3. For each operator with an effect Eff with a postcondition EffCond that can unify with Cond:
   • Instantiate a new step Step;
   • Complete the link Open by using Eff as the establishing effect;
   • Add the enabling preconditions of Step as open conditions;
   • Add the resulting partial plan to NewPlans;
4. For each plan in NewPlans:
   • Add an ordering to ensure that Step precedes SupStep;
   • Add the bindings necessary to ensure that EffCond unifies with Cond;
   • Add the secondary preconditions SecPre of Eff as open conditions;
   • Propagate labels as appropriate;
5. Return NewPlans.

1. Initialize list NewCPlans;
2. If Uncertainty is a new source of uncertainty in the plan:
   • Add a new decision-step DecStep for uncertainty Uncertainty;
   • Add new top-level goals as open conditions with the appropriate labels;
   • Add the resulting partial plan to NewCPlans;
3. If Uncertainty is an existing source of uncertainty in the plan:
   • Find an existing decision-step DecStep for uncertainty Uncertainty;
   • Add the resulting partial plan to NewCPlans;
4. For each plan in NewCPlans:
   • Modify the decision-rule in DecStep for Outcome to include Cond as an antecedent;
   • Add (know-if Cond) as an open condition required to establish DecStep;
   • Add orderings to ensure that DecStep precedes SupStep;
   • Propagate labels as appropriate;
5. Return NewCPlans.