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Jadex Rules is a small lightweight rule engine, which currently employs the well-known Rete algorithm for highly efficient rule matching. Jadex rules is therefore similar to other rule engines like JESS and Drools. Despite the similarities there are also important differences between these systems: * Jadex Rules is very small and intended to be used as component of other software. Even though rules can be specified in a Java dialect as well as (a small variation of) the CLIPS language its primary usage is on the API level. Jadex Rules is currently the core component of the Jadex BDI reasoning engine. * Jadex Rules cleanly separates between state and rule representation. This allows the state implementation as well as the matcher to be flexibly exchanged. Some experiments have e.g. been conducted with a Jena representation. Regarding the matcher, it is planned to support also the Treat algorithm, which has a lower memory footprint than Rete. * Jadex Rules pays close attention to rule debugging. The state as well as the rete engine can be observed at runtime. The rule debugger provides functionalities to execute a rule program stepwise and also use rule breakpoints to stop the execution at those points.

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package jadex.rules.rulesystem.rete.nodes;

import java.util.Collection;
import java.util.Iterator;

import jadex.rules.rulesystem.AbstractAgenda;
import jadex.rules.rulesystem.rete.Tuple;
import jadex.rules.rulesystem.rete.constraints.ConstraintIndexer;
import jadex.rules.rulesystem.rete.constraints.IConstraintEvaluator;
import jadex.rules.state.IOAVState;
import jadex.rules.state.OAVAttributeType;

/**
 *  A beta node has the purpose to perform a constraints check
 *  between (at least) two objects. The beta node has to incoming
 *  coming connections which both can activate the node.
 */
public class BetaNode extends AbstractBetaNode
{
	//-------- constructors --------
	
	/**
	 *  Create a new beta node.
	 */
	public BetaNode(int nodeid, IConstraintEvaluator[] evaluators, ConstraintIndexer[] xevaluators)
	{
		super(nodeid, evaluators, xevaluators);
	}
	
	//-------- tuple consumer interface (left) --------
	
	/**
	 *  Modify a tuple in this node.
	 *  @param left The tuple.
	 */
	public void modifyTuple(Tuple left, int tupleindex, OAVAttributeType type,
		Object oldvalue, Object newvalue, IOAVState state, ReteMemory mem, AbstractAgenda agenda)
	{
		if(!getRelevantAttributes().contains(type))
			return;

		super.modifyTuple(left, tupleindex, type, oldvalue, newvalue, state, mem, agenda);

		if(!isAffected(type))
		{
			Collection omem = fetchObjectMemory(state, left, mem);
			if(omem!=null)
			{
				for(Iterator it=omem.iterator(); it.hasNext(); )
				{
					Object	right = it.next();
					boolean	contains = isMatchContained(state, left, right, mem);
				
					// Tuple changed in memory -> propagate modification
					if(contains)
						propagateModification(left, right, tupleindex, type, oldvalue, newvalue, state, mem, agenda);
				}
			}
		}
	}
	
	//-------- object consumer interface (right) --------
	
	/**
	 *  Propagate an object change to this node.
	 *  @param right The new object.
	 */
	public void modifyObject(Object right, OAVAttributeType type, Object oldvalue, Object newvalue, IOAVState state, ReteMemory mem, AbstractAgenda agenda)
	{
		if(!getRelevantAttributes().contains(type))
			return;

		super.modifyObject(right, type, oldvalue, newvalue, state, mem, agenda);
		
		if(!isAffected(type))
		{
			Collection tmem = fetchTupleMemory(state, right, mem);
			if(tmem!=null)
			{
				for(Iterator it=tmem.iterator(); it.hasNext(); )
				{
					Tuple	left = (Tuple)it.next();
					boolean	contains = isMatchContained(state, left, right, mem);
				
					// Tuple changed in memory -> propagate modification
					if(contains)
						propagateModification(left, right, left.size(), type, oldvalue, newvalue, state, mem, agenda);
				}
			}
		}
	}
	
	//-------- template methods --------

	/**
	 *  Add a match to the node memory and propagate if necessary.
	 */
	protected void addMatch(Tuple left, Object right, IOAVState state, ReteMemory mem, AbstractAgenda agenda)
	{
		Tuple result = mem.getTuple(state, left, right);
		BetaMemory bmem = (BetaMemory)mem.getNodeMemory(this);
		if(bmem.addResultTuple(result))
		{
			ITupleConsumerNode[] tcs = tconsumers;
			for(int j=0; tcs!=null && j