diff -u -r1.2 -r1.3
--- ITrackerHit.java	15 Sep 2008 15:44:02 -0000	1.2
+++ ITrackerHit.java	18 Sep 2008 23:17:08 -0000	1.3
@@ -12,7 +12,7 @@

  * Interface to represent a hit in the tracker.
  *
  * @author D. Onoprienko

- * @version $Id: ITrackerHit.java,v 1.2 2008/09/15 15:44:02 onoprien Exp $

+ * @version $Id: ITrackerHit.java,v 1.3 2008/09/18 23:17:08 onoprien Exp $

  */
 public interface ITrackerHit extends Identifiable {
   

@@ -86,15 +86,37 @@

 
   /**
    * Enumeration of hit types.

+   * <p>
+   * This class defines a set of static constants that are used to identify different
+   * types of <tt>ITrackerHit</tt>. Custom types can be added by subclassing this class 
+   * and defining new constants.
+   * <p>
+   * Public methods of this class can be used to find out, for each of the axes of the
+   * hit's local reference frame, whether the hit's position along that axis direction is
+   * measured, unmeasured, or fixed. 
+   * <p>
+   * "Unmeasured" means the hit has a finite size along
+   * this direction. The size value can be retrieved by calling {@link ITrackerHit#getDimensions()}.
+   * For <tt>STRIP</tt>, for example, V is unmeasured, and the hit dimension along V is
+   * equal to the length of the strip.
+   * <p>
+   * "Fixed" means the hit is projected to the reference surface perpendicular to the given 
+   * axis, so the measurement error along this direction is zero.

    */
   public class Type {
     
     protected enum Dir {MEASURED, UNMEASURED, FIXED};
     

+    /** Unknown type marker. */

     static public final Type UNKNOWN = new Type(Dir.UNMEASURED, Dir.UNMEASURED, Dir.UNMEASURED);

+    /** Hit in silicon pixels sensor. U is measured, V is measured, W is fixed. */

     static public final Type PIXEL = new Type(Dir.UNMEASURED, Dir.UNMEASURED, Dir.UNMEASURED);

+    /** Hit in silicon strips sensor. U is measured, V is unmeasured, W is fixed. */

     static public final Type STRIP = new Type(Dir.UNMEASURED, Dir.UNMEASURED, Dir.UNMEASURED);

+    /** Stereo cross between two strips. U is measured, V is measured, W is fixed. */

     static public final Type CROSS = new Type(Dir.UNMEASURED, Dir.UNMEASURED, Dir.UNMEASURED);

+    /** Generic 3-dimensional hit. All three coordinates are measured. */
+    static public final Type D3 = new Type(Dir.MEASURED, Dir.MEASURED, Dir.MEASURED);

     
     private int _nM, _nU, _nF;
     private boolean[] _isM, _isU, _isF;

@@ -139,8 +161,6 @@

     /**
      * Returns <tt>true</tt> if the position along the axis specified by the argument
      * (in local reference frame: 0 = U, 1 = V, 2 = W) is fixed for this type of hit.

-     * "Fixed" means the hit is projected to the reference surface perpendicular to the 
-     * given axis, so the measurement error along this direction is zero.

      */
     public boolean isFixed(int axis) {return _isF[axis];}
   }