/// <summary>
/// Checks whether the operator effects are relevant to the given target conditions.
/// </summary>
/// <param name="conditions">Conditions for the application.</param>
/// <param name="operatorPreconditions">Operator preconditions.</param>
/// <returns>True if the operator effects are relevant to the given conditions, false otherwise.</returns>
public bool IsRelevant(IConditions conditions, ISimpleConditions operatorPreconditions)
{
// Besides the effects relevance, we need to check whether the operator preconditions are not in conflict with the resulting
// conditions (after backward-apply). This can be done via affected variables: if some effect is relevant, then it modifies a
// variable, and a constraint corresponding to this variable can be removed from the preconditions. At the end, we check the
// modified precondition constraints with the target conditions and if there are conflicts, we consider the operator not
// relevant. This approach works even for conditional-effects, because we take the worst case scenario.
IConditions nonAffectedPreconditions = (IConditions)operatorPreconditions.Clone();
bool anyRelevant = false;
foreach (var effect in this)
{
var relevance = effect.IsRelevant(conditions);
if (relevance == EffectRelevance.ANTI_RELEVANT)
{
return(false);
}
else if (relevance == EffectRelevance.RELEVANT)
{
anyRelevant = true;
nonAffectedPreconditions.RemoveConstraint(effect.GetAssignment());
}
}
return(anyRelevant && !nonAffectedPreconditions.IsConflictedWith(conditions));
}
/// <summary>
/// Applies the effect backwards to the given conditions.
/// </summary>
/// <param name="conditions">Conditions.</param>
public virtual IConditions ApplyBackwards(IConditions conditions)
{
if (!conditions.IsConflictedWith(Assignment))
{
conditions.RemoveConstraint(Assignment);
return(conditions);
}
return(new ConditionsContradiction());
}
/// <summary>
/// Applies the effect backwards to the given conditions.
/// </summary>
/// <param name="conditions">Conditions.</param>
public override IConditions ApplyBackwards(IConditions conditions)
{
if (IsRelevant(conditions) == EffectRelevance.RELEVANT)
{
IConditions newConditions = (IConditions)conditions.Clone();
newConditions.RemoveConstraint(Assignment);
newConditions = newConditions.ConjunctionWith(Conditions);
return(conditions.DisjunctionWith(newConditions));
}
return(conditions);
}
/// <summary>
/// Checks whether the operator effect is relevant to the given target conditions.
/// </summary>
/// <param name="conditions">Conditions.</param>
/// <returns>Effect relevance result.</returns>
public override EffectRelevance IsRelevant(IConditions conditions)
{
var assignmentRelevance = base.IsRelevant(conditions);
if (assignmentRelevance == EffectRelevance.RELEVANT)
{
IConditions nonAffectedConditions = (IConditions)Conditions.Clone();
nonAffectedConditions.RemoveConstraint(Assignment);
if (!nonAffectedConditions.IsConflictedWith(conditions))
{
return(EffectRelevance.RELEVANT);
}
}
// conditional effect does not have to be used, so it should never be explicitly anti-relevant
return(EffectRelevance.IRRELEVANT);
}