interface event 
  {
  protected :
    event(int qp=0,int sp=0,int kf = FALSE);   // constructor
  
  public :
    virtual ~event();  // destructor.
  
    virtual int operator()() = 0;  // abstract.
  
    virtual int verify();  // abstract
  
    int report(histogram* h,double interval = 0); // generate report
  
    void stamp();           // add time stamp.
    double timespent();     // return time since the stamp.
  
    int queuingpriority();           // return queuing priority.
    void queuingpriority(int p);     // adjust queuing priority.
    int schedulingpriority();        // return scheduling priority.
    void schedulingpriority(int p);  // adjust scheduling priority.
  
    int active();          // is active ?
    int pending();         // is pending ?
    int conditional();     // is conditional ?
    int closed();          // is closed ?
    int passive();         // is passive ?
    int queued();          // is queued ?
  };