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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.state.javaimpl;

import jadex.rules.state.OAVTypeModel;

import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;

/**
 *  An object holding the state as
 *  OAV triples (object, attribute, value).
 */
public class OAVContentIdState	extends OAVAbstractState
{
	//-------- attributes --------
	
	/** The objects table. */
	protected Set objects;
	
	//-------- constructors --------
	
	/**
	 *  Create a new empty OAV state representation.
	 */
	public OAVContentIdState(OAVTypeModel tmodel)
	{
		super(tmodel);
		this.objects = new LinkedHashSet();
	}
	
	/**
	 *  Create an id generator.
	 *  @return The id generator.
	 */
	public IOAVIdGenerator createIdGenerator()
	{
//		return new OAVLongIdGenerator(true);
//		return new OAVNameIdGenerator(true);
		return new OAVDebugIdGenerator(true);
//		return new OAVObjectIdGenerator(true);
	}
	
	//-------- object management --------
	
	/**
	 *  Add an external usage of a state object (oid). This prevents
	 *  the oav object of being garbage collected as long
	 *  as external references are present.
	 *  @param id The oav object id.
	 *  @param external The user object.
	 */
	public void addExternalObjectUsage(Object id, Object external)
	{
		// #ifndef MIDP
		if(!generator.isId(id))
			System.out.println("driss: "+id);
		assert nocheck || generator.isId(id);
		// #endif
	}
	
	/**
	 *  Remove an external usage of a state object (oid). This allows
	 *  the oav object of being garbage collected when no
	 *  further external references and no internal references
	 *  are present.
	 *  @param id The oav object id.
	 *  @param external The state external object.
	 */
	public void removeExternalObjectUsage(Object id, Object external)
	{
		// #ifndef MIDP
		assert nocheck || generator.isId(id);
		// #endif
	}
	
	/**
	 *  Test if an object is externally used.
	 *  @param id The id.
	 *  @return True, if externally used.
	 */
	protected boolean isExternallyUsed(Object id)
	{
		return false;
	}
	
	//-------- internal object handling --------
	
	/**
	 *  Internally create an object.
	 *  @param id The id.
	 *  @return The content map of the new object.
	 */
	protected Map internalCreateObject(Object id)
	{
		objects.add(id);
		return ((IOAVContentId)id).getContent();
	}
	
	/**
	 *  Remove an object from the state objects.
	 *  @param id The id.
	 *  @return The content map of the object.
	 */
	protected Map internalRemoveObject(Object id)
	{
		objects.remove(id);
		return ((IOAVContentId)id).getContent();
	}
	
	/**
	 *  Get the object content of an object.
	 *  @param id The id.
	 *  @return The content map of the object.
	 */
	protected Map internalGetObjectContent(Object id)
	{
		return ((IOAVContentId)id).getContent();
	}
	
	/**
	 *  Test if an object is contained in the state.
	 *  @param id The id.
	 *  @return True, if object is contained.
	 */
	protected boolean internalContainsObject(Object id)
	{
		return objects.contains(id);
	}
	
	/**
	 *  Test how many object are contained in the state.
	 *  @return The number of objects.
	 */
	protected int internalObjectsSize()
	{
		return objects.size();
	}
	
	/**
	 *  Get a set of the internal state objects.
	 *  @return A set of the state objects. 
	 */
	protected Set internalGetObjects()
	{
		return objects;
	}

	/**
	 *  Test if reading the object (oid) is allowed.
	 *  Reading is allowed on removed objects as long as there are external references.
	 *  @param id The object (oid).
	 *  @return True, if valid.
	 */
	protected boolean checkValidStateObjectRead(Object id)
	{
		// #ifndef MIDP
		assert nocheck || generator.isId(id);
		// #endif

		return true;	// Hack!!! Needed, because isExternallyUsed always returns false.
	}
}