//backward chain
public Clause Infer(string goal_variable, List <Clause> unproved_conditions)
{
Clause conclusion = null;
List <Rule> goal_stack = new List <Rule>();
foreach (Rule rule in m_rules)
{
Clause consequent = rule.getConsequent();
if (consequent.Variable == goal_variable)
{
goal_stack.Add(rule);
}
}
foreach (Rule rule in goal_stack)
{
rule.FirstAntecedent();
bool goal_reached = true;
while (rule.HasNextAntecedents())
{
Clause antecedent = rule.NextAntecedent();
if (!m_wm.IsFact(antecedent))
{
if (m_wm.IsNotFact(antecedent)) //conflict with memory
{
goal_reached = false;
break;
}
else if (IsFact(antecedent, unproved_conditions)) //deduce to be a fact
{
m_wm.AddFact(antecedent);
}
else //deduce to not be a fact
{
goal_reached = false;
break;
}
}
}
if (goal_reached)
{
conclusion = rule.getConsequent();
break;
}
}
return(conclusion);
}
//backward chain
public Clause Infer(string goal_variable, List <Clause> unproved_conditions)
{
Clause conclusion = null;
List <Rule> goal_stack = new List <Rule>();
foreach (Rule rule in m_rules)
{
Clause consequent = rule.getConsequent();
if (consequent.Variable == goal_variable)
{
goal_stack.Add(rule);
}
}
foreach (Rule rule in goal_stack)
{
rule.FirstAntecedent();
bool goal_reached = true;
while (rule.HasNextAntecedents())
{
Clause antecedent = rule.NextAntecedent();
if (!m_wm.IsFact(antecedent))
{
if (m_wm.IsNotFact(antecedent)) //conflict with memory
{
goal_reached = false;
break;
}
else if (IsFact(antecedent, unproved_conditions)) //deduce to be a fact
{
string facts = string.Empty;
foreach (var fact in m_wm._facts)
{
facts += $" {fact}";
}
JustificationSingleton.WriteLine($"{facts}->{antecedent}\n\n");
m_wm.AddFact(antecedent);
}
else //deduce to not be a fact
{
goal_reached = false;
break;
}
}
}
if (goal_reached)
{
conclusion = rule.getConsequent();
string facts = string.Empty;
foreach (var fact in m_wm._facts)
{
facts += $" {fact}";
}
JustificationSingleton.WriteLine($"{facts}->{conclusion}\n");
break;
}
}
return(conclusion);
}