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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.
package jadex.rules.rulesystem;
import jadex.rules.rulesystem.rules.IPriorityEvaluator;
import jadex.rules.state.IOAVState;
/**
* An activation is a rule and an associated fact
* tuple which represents a full match.
* Activations are created from terminal nodes
* and will be added to the agenda.
*/
public class Activation
{
//-------- attributes --------
/** The rule. */
protected IRule rule;
/** The values. */
protected IVariableAssignments values;
/** The state. */
protected IOAVState state;
/** The priority. */
protected int priority;
protected boolean inited;
//-------- constructors --------
/**
* Create a new Activation.
* @param rule The rule.
*/
public Activation(IRule rule, IVariableAssignments values, IOAVState state)
{
this.rule = rule;
this.values = values;
this.state = state;
}
//-------- methods --------
/**
* Get the rule.
* @return The rule.
*/
public IRule getRule()
{
return rule;
}
/**
* Get the variable assignments.
*/
public IVariableAssignments getVariableAssignments()
{
return values;
}
/**
* Get the priority.
* @return The priority.
*/
public int getPriority()
{
if(!inited)
{
IPriorityEvaluator pe = rule.getPriorityEvaluator();
if(pe!=null)
priority = pe.getPriority(state, values);
inited = true;
}
return priority;
}
/**
* Execute the activation.
*/
public void execute()
{
getRule().getAction().execute(state, values);
}
/**
* Get the hashcode of this object.
* @return The hashcode.
*/
public int hashCode()
{
int result = 31 * rule.hashCode();
result = 31 * result + values.hashCode();
return result;
}
/**
* Test if two activations are equal.
* @param o The object to test.
*/
public boolean equals(Object o)
{
if(o==this)
return true;
boolean ret = false;
if(o instanceof Activation)
{
Activation act = (Activation)o;
ret = rule.equals(act.getRule()) && values.equals(act.values);
}
return ret;
}
/**
* Create a string representation of the activation.
*/
public String toString()
{
return "Activation(rule="+rule.getName()+", values="+values+", priority="+priority+")";
// return "Activation(rule="+rule.getName()+" priority="+priority+" "+values.hashCode()+")";
}
}