// fixme: Not sure yet how to handle real-time issues. Don't want this loop to spin endlessly, will need it to yield so other processes
// can run. For a simple lexeme-based CSA, the presenter could be where the yield lives. Another option is to not have Execute() be a loop.
// Instead use an event-based architecture where changes to the blackboard trigger the controller. For now, just select a single KS and
// execute it. Punt looping to the enclosing application.
public void Execute()
{
UpdateAgenda();
IKnowledgeSourceActivation selectedKSA = SelectKSForExecution();
if (selectedKSA != null)
{
selectedKSA.Execute();
m_Agenda.Remove(selectedKSA);
}
}
// fixme: selects the highest priority KSA for execution. More generally, would want to select KSs probabilistically based on priority.
// Consider implementing controllers with KSAs on their own blackboard. There's a regress where the KSs that implement a controller need
// their own meta-controller to decide what to do. This regress can be broken by having "eager" KSs that execute immediately when their
// preconditions are satisfied (like a forward-chaining rule).
protected override IKnowledgeSourceActivation SelectKSForExecution()
{
IKnowledgeSourceActivation highestPriorityKSA = null;
int highestPriority = int.MinValue;
foreach (IKnowledgeSourceActivation KSA in m_Agenda)
{
Debug.Assert(KSA.Properties.ContainsKey(Priority));
int curPriority = (int)KSA.Properties[Priority];
if (curPriority > highestPriority)
{
highestPriorityKSA = KSA;
highestPriority = curPriority;
}
}
return(highestPriorityKSA); // returns null if there are no KSs in the agenda
}
public override IKnowledgeSourceActivation[] Precondition()
{
// Use LINQ to create a collection of the requested U_PrologEvalQueries on the blackboard.
var requests = from request in m_blackboard.LookupUnits <U_PrologEvalRequest>() // Lookup ID select requests
where // where the request has not been previously matched by this knowledge source precondition
(!request.Slots.ContainsKey(KSPreconditionMatched)) ||
(!((ISet <ReactiveKnowledgeSource>)request.Slots[KSPreconditionMatched]).Contains(this))
select request;
IKnowledgeSourceActivation[] activations = new IKnowledgeSourceActivation[requests.Count()];
// Currently only support one prolog KB
// fixme: eventually may want to support multiple prolog KBs so will need mechanism for supporting them as well as inheritance
var prologKB = m_blackboard.LookupSingleton <U_PrologKB>(); // Lookup prolog kbs.
// Iterate through each of the requests, creating KnowledgeSourceActivations
int i = 0;
foreach (var request in requests)
{
var boundVars = new Dictionary <string, object>
{
[PrologEvalRequest] = request,
[PrologKB] = prologKB
};
activations[i++] = new KnowledgeSourceActivation(this, boundVars);
// fixme: this bit of boilerplate code for marking a knowledge unit as having already participated in a matched precondition
// should be baked into the infrastructure somewhere so knowledge source implementers don't always have to do this.
// A good place to add this would be on Unit (and declare a method on IUnit).
if (request.Slots.ContainsKey(KSPreconditionMatched))
{
((HashSet <ReactiveKnowledgeSource>)request.Slots[KSPreconditionMatched]).Add(this);
}
else
{
request.Slots[KSPreconditionMatched] = new HashSet <ReactiveKnowledgeSource> {
this
};
}
}
return(activations);
}
public override IKnowledgeSourceActivation[] Precondition()
{
// Use LINQ to create a collection of the requested U_IDQueries on the blackboard.
var requests = from request in m_blackboard.LookupUnits <U_IDSelectRequest>() // Lookup ID queries
where // where the query has not been previously matched by this knowledge source precondition
(!request.Slots.ContainsKey(KSPreconditionMatched)) ||
(!((ISet <ReactiveKnowledgeSource>)request.Slots[KSPreconditionMatched]).Contains(this))
select request;
IKnowledgeSourceActivation[] activations = new IKnowledgeSourceActivation[requests.Count()];
// Iterate through each of the queries, creating KnowledgeSourceActivations
int i = 0;
foreach (var request in requests)
{
var boundVars = new Dictionary <string, object>
{
[IDSelectRequest] = request
};
activations[i++] = new KnowledgeSourceActivation(this, boundVars);
// fixme: this bit of boilerplate code for marking a knowledge unit as having already participated in a matched precondition
// should be baked into the infrastructure somewhere so knowledge source implementers don't always have to do this.
// A good place to add this would be on Unit (and declare a method on IUnit).
if (request.Slots.ContainsKey(KSPreconditionMatched))
{
((HashSet <ReactiveKnowledgeSource>)request.Slots[KSPreconditionMatched]).Add(this);
}
else
{
request.Slots[KSPreconditionMatched] = new HashSet <ReactiveKnowledgeSource> {
this
};
}
}
return(activations);
}
/*public*/
void TestSelectKSForExecution_PriorityController()
{
PriorityController_PublicMethods controller = new PriorityController_PublicMethods();
IBlackboard blackboard = new Blackboard();
KS_Old_ReactiveIDSelector ks1 = new KS_Old_ReactiveIDSelector(blackboard);
KS_Old_ReactiveIDSelector ks2 = new KS_Old_ReactiveIDSelector(blackboard);
KS_Old_ReactiveIDSelector ks3 = new KS_Old_ReactiveIDSelector(blackboard);
ks1.Properties[Priority] = 10;
ks2.Properties[Priority] = 30;
ks3.Properties[Priority] = 20;
controller.AddKnowledgeSource(ks1);
controller.AddKnowledgeSource(ks2);
controller.AddKnowledgeSource(ks3);
blackboard.AddUnit(new U_IDSelectRequest("foo"));
controller.UpdateAgenda();
Assert.Equal(3, controller.Agenda.Count);
IKnowledgeSourceActivation KSA = controller.SelectKSForExecution();
Assert.Equal(30, KSA.Properties[KSProps.Priority]);
}