--- a/flys-artifacts/ChangeLog	Fri Sep 16 10:49:04 2011 +0000
+++ b/flys-artifacts/ChangeLog	Fri Sep 16 11:30:50 2011 +0000
@@ -1,3 +1,10 @@
+2011-09-16  Felix Wolfsteller <felix.wolfsteller@intevation.de>
+
+ Take a given WaterlevelPair-String, load artifact and plot the diff.
+
+	* src/main/java/de/intevation/flys/artifacts/state/WDifferencesState.java:
+	  Load correct artifacts.
+
 2011-09-16  Bjoern Schilberg <bjoern.schilberg@intevation.de>
 
 	* doc/mapserver/*: Added inital mapserver configuration files.

--- a/flys-artifacts/src/main/java/de/intevation/flys/artifacts/states/WDifferencesState.java	Fri Sep 16 10:49:04 2011 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/artifacts/states/WDifferencesState.java	Fri Sep 16 11:30:50 2011 +0000
@@ -22,7 +22,6 @@
 
 import de.intevation.flys.utils.FLYSUtils;
 
-//import net.sf.json.JSONObject;
 
 public class WDifferencesState
 extends      DefaultState
@@ -44,6 +43,25 @@
 
 
     @Override
+    public boolean validate(Artifact artifact)
+    throws IllegalArgumentException
+    {
+        FLYSArtifact flys = (FLYSArtifact) artifact;
+
+        StateData data = flys.getData("diffids");
+
+        if (data == null) {
+            throw new IllegalArgumentException("diffids is empty");
+        }
+
+        // TODO: Also validate format.
+
+        return true;
+    }
+
+
+
+    @Override
     public Object computeAdvance(
         FLYSArtifact artifact,
         String       hash,
@@ -54,16 +72,30 @@
         WINFOArtifact winfo = (WINFOArtifact)artifact;
         String id = getID();
 
-        // Get a data item (uuids) or parameterization of the respective
-        // artifacts.
-        // TODO Fix, choose artifacts/parameterization dynamically.
+        // Load the Artifacts/facets that we want to subtract and display.
+        // Expected format is:
+        // [42537f1e-3522-42ef-8968-635b03d8e9c6;longitudinal_section.w;0]#[1231f2-....]
+        String datas[] = winfo.getDataAsString("diffids");
+
+        // Validate the Data-Strings.
+        for (String s: datas) {
+            if (!WaterlevelSelectState.isValid(winfo.getDataAsString("diffids"))) {
+                // TODO: escalate.
+            }
+        }
+
+        if (datas.length != 2) {
+            // TODO crash with style
+            ;
+        }
+        String uuid1 = WaterlevelSelectState.strip(datas[0]).split(";")[0];
+        String uuid2 = WaterlevelSelectState.strip(datas[1]).split(";")[0];
+
         WINFOArtifact flys1 = (WINFOArtifact) FLYSUtils.getArtifact(
-            //"a110a16d-d155-4115-ab0d-c4c61101c9cb", //Collection
-            "a0ec533f-b05b-4dcd-9db3-7850686f90a2",
+            uuid1,
             context);
         WINFOArtifact flys2 = (WINFOArtifact) FLYSUtils.getArtifact(
-            //"8ebb696d-771a-4540-bd18-15e19744a6e2", //Collection
-            "ce5a2c4e-3f9c-4c4d-a35c-109dd8670992",
+            uuid2,
             context);
 
         if (flys1 == null) {
@@ -83,14 +115,13 @@
             wkms = WKmsOperation.SUBTRACTION.operate(minuend[0], subtrahend[0]);
             facetName = "W ("+minuend[0].getName() + ") - W (" + subtrahend[0].getName()+")";
             logger.warn("Did a WKMSSubtraction");
-            // Add these datasets also as facets.
-            // TODO Store parameterization.
-            // Therefore need: getKmRange, getQs, getRiver, eventually getWs
+            // Add these datasets also as facets ("absolutes").
+            /*
             Facet minuendAbsFacet = new WaterlevelFacet(0, LONGITUDINAL_W,
                 "Minuend: W (_todo_)", ComputeType.ADVANCE, id, hash);
             Facet subtrahendAbsFacet = new WaterlevelFacet(1, LONGITUDINAL_W,
                 "Subtrahend: W (_todo_)", ComputeType.ADVANCE, id, hash);
-            //JSONObject jsonObject = new JSONObject().accumulate("string", 2.0f);
+            */
             //facets.add(minuendAbsFacet);
             //facets.add(subtrahendAbsFacet);
         }