--- a/artifact-database/src/main/java/de/intevation/artifactdatabase/state/DefaultFacet.java	Wed Nov 23 17:17:39 2011 +0000
+++ b/artifact-database/src/main/java/de/intevation/artifactdatabase/state/DefaultFacet.java	Wed Nov 30 08:13:48 2011 +0000
@@ -1,5 +1,7 @@
 package de.intevation.artifactdatabase.state;
 
+import java.util.List;
+
 import org.w3c.dom.Document;
 import org.w3c.dom.Element;
 import org.w3c.dom.Node;
@@ -18,18 +20,21 @@
  */
 public class DefaultFacet implements Facet {
 
-    /** The index of this facet.*/
+    /** The index of this facet. */
     protected int index;
 
-    /** The name of this facet.*/
+    /** The name of this facet. */
     protected String name;
 
-    /** The description of this facet.*/
+    /** The description of this facet. */
     protected String description;
 
+
+    /** Trivial, empty constructor. */
     public DefaultFacet() {
     }
 
+
     /**
      * The default constructor to create new Facet objects.
      *
@@ -54,12 +59,17 @@
         this.description = description;
     }
 
+
+    /**
+     * Copies name, index and description of other facet.
+     */
     public void set(Facet other) {
         index       = other.getIndex();
         name        = other.getName();
         description = other.getDescription();
     }
 
+
     public Facet deepCopy() {
         DefaultFacet copy = new DefaultFacet();
         copy.set(this);
@@ -82,10 +92,38 @@
     }
 
 
+    /**
+     * @return null
+     */
     public Object getData(Artifact artifact, CallContext context) {
         return null;
     }
 
+
+    /**
+     * (Do not) provide data.
+     * Override to allow other facets to access your data.
+     * @return always null.
+     */
+    public Object provideBlackboardData(
+        Artifact artifact,
+        Object key,
+        Object param,
+        CallContext context
+    ) {
+        return null;
+    }
+
+
+    /**
+     * Return list of keys (objects) for which this facet can provide data
+     * ("external parameterization"), for other facets, via blackboard.
+     */
+    public List getDataProviderKeys() {
+        return null;
+    }
+
+
     public String toString() {
         return new StringBuilder("name = '")
             .append(name).append("', index = ")