//Determine KB logic based on given model
public bool isTrue(knowledgeBase kB)
{
bool kbLogic = true;
foreach (sentence s in kB.Sentences)
{
kbLogic = kbLogic && isTrue(s);
}
return(kbLogic);
}
//Check all models based on given symbols
public void CheckAll(knowledgeBase kB, sentence query, List <propositionalSymbol> symbols, model model)
{
if (symbols.Count == 0)
{
if (model.isTrue(kB))
{
if (model.isTrue(query))
{
modelEntailments++;
}
//return model.isTrue(query);
}
//else return true;
}
else
{
propositionalSymbol s = new propositionalSymbol(symbols.First());
//rest of the symbols
List <propositionalSymbol> rest = new List <propositionalSymbol>();
rest.AddRange(symbols);
rest.RemoveAt(0);
//Initialize model for true branch
model mleft = new model();
mleft.getCellList.AddRange(model.getCellList);
mleft.getCellList.Add(new cell(s, true));
//Initialize model for false branch
model mright = new model();
mright.getCellList.AddRange(model.getCellList);
mright.getCellList.Add(new cell(s, false));
//Recursive call
CheckAll(kB, query, rest, mleft);
CheckAll(kB, query, rest, mright);
}
}
//Backward chaining algorithm
public bool BCEntails(knowledgeBase kB, sentence query)
{
//Initialize list for storing implication clause only
List <sentence> implication = new List <sentence>();
int factsCount;
//Add query to open list
if (!open.Any(x => x.getSymbol == query.Symbols.First().getSymbol))
{
open.Add(query.Symbols.First());
}
//Return false if the query is not an atomic sentence
if (!query.isAtomicSentence())
{
return(false);
}
//Construct simpler sentences in each KB sentences and add atomic sentences to known facts list
foreach (sentence s in kB.Sentences)
{
if (!s.isAtomicSentence())
{
if (s.Children.Count == 0)
{
s.constructChildren();
}
implication.Add(s);
}
else
{
if (!facts.Any(x => x.getSymbol == s.Symbols.First().getSymbol))
{
facts.Add(s.Symbols.First());
}
}
}
//If the query is a known fact in KB
if (facts.Any(x => x.getSymbol == query.Symbols.First().getSymbol))
{
trace.Add(query.Symbols.First());
return(true);
}
//Return false if the query is not a conclusion of any of KB sentences
if (!implication.Any(x => x.Children.Last().Symbols.First().getSymbol == query.Symbols.First().getSymbol))
{
return(false);
}
//Loop through KB
foreach (sentence s in implication)
{
//Check if query match any conclusions in KB
if (s.Children.Last().Symbols.Any(x => x.getSymbol == query.Symbols.First().getSymbol))
{
//Check whether if conjunction premise consists of only one single atomic sentence
if (s.Children.First().isAtomicSentence())
{
//Check if
if (!facts.Any(x => x.getSymbol == s.Children.First().Symbols.First().getSymbol))
{
if (!open.Any(x => x.getSymbol == s.Children.First().Symbols.First().getSymbol))
{
open.Add(s.Children.First().Symbols.First());
}
}
else
{
//Check for duplication
if (!trace.Any(x => x.getSymbol == s.Children.First().Symbols.First().getSymbol))
{
trace.Add(s.Children.First().Symbols.First());
}
trace.Add(query.Symbols.First());
facts.Add(query.Symbols.First());
open.RemoveAll(x => x.getSymbol == query.Symbols.First().getSymbol);
}
}
else
{
factsCount = 0;
foreach (propositionalSymbol p in s.Children.First().Symbols)
{
//Check if symbol is still yet to be known
if (open.Any(x => x.getSymbol == p.getSymbol))
{
agenda.Enqueue(p);
continue;
}
//Check if each symbol in conjunction premise is a known fact
if (facts.Any(x => x.getSymbol == p.getSymbol))
{
if (!trace.Any(x => x.getSymbol == p.getSymbol))
{
trace.Add(p);
}
factsCount++;
}
//Check if conjunction premise fully consists of known facts
if (factsCount == s.Children.First().Symbols.Count)
{
facts.Add(s.Children.Last().Symbols.First());
trace.Add(s.Children.Last().Symbols.First());
open.RemoveAll(x => x.getSymbol == s.Children.Last().Symbols.First().getSymbol);
}
//Check if symbol is already inferred
if (!trace.Any(x => x.getSymbol == p.getSymbol))
{
open.Add(p);
agenda.Enqueue(p);
}
}
}
}
}
//Make recursive call as long as there is more to expand in the agenda or open list
if (agenda.Count != 0)
{
return(BCEntails(kB, new sentence(agenda.Dequeue())));
}
else
{
if (open.Count == 0)
{
return(true);
}
else
{
sentence openPullFirst = new sentence(open.First());
open.Remove(open.First());
return(BCEntails(kB, openPullFirst));
}
}
}
//Forward chaining algorithm
public bool FCEntails(knowledgeBase kB, sentence query)
{
Dictionary <sentence, int> count = new Dictionary <sentence, int>();
Queue <propositionalSymbol> agenda = new Queue <propositionalSymbol>();
propositionalSymbol p;
List <sentence> hornClause = new List <sentence>();
//Construct simpler sentences in each KB sentences and allocate KB atomic sentences into agenda
foreach (sentence s in kB.Sentences)
{
if (!s.isAtomicSentence())
{
s.constructChildren();
}
else
{
agenda.Enqueue(s.Symbols.Last());
}
}
//Allocate horn clause list from KB
foreach (sentence s in kB.Sentences)
{
if (s.isImplicationClause())
{
hornClause.Add(s);
}
}
//Count number of symbols on conjunction side
foreach (sentence s in hornClause)
{
count.Add(s, s.Children.First().Symbols.Count);
}
while (agenda.Count != 0)
{
p = agenda.Dequeue();
if (!InferredSymbols.Contains(p))
{
inferred.Add(p);
foreach (sentence s in hornClause)
{
if (s.Children.First().Symbols.Any(x => x.getSymbol == p.getSymbol))
{
count[s]--;
if (count[s] == 0)
{
if (s.Symbols.Last().getSymbol == query.Symbols.First().getSymbol)
{
inferred.Add(s.Symbols.Last());
return(true);
}
agenda.Enqueue(s.Symbols.Last());
}
}
}
}
}
return(false);
}
//Check entailment of alpha from KB
public void Entails(knowledgeBase kB, sentence query, List <propositionalSymbol> symbols)
{
CheckAll(kB, query, symbols, new model());
}