--- a/artifacts/src/main/java/org/dive4elements/river/artifacts/model/sq/SQ.java	Thu Aug 08 12:06:54 2013 +0200
+++ b/artifacts/src/main/java/org/dive4elements/river/artifacts/model/sq/SQ.java	Thu Aug 08 12:17:03 2013 +0200
@@ -11,8 +11,37 @@
 import java.io.Serializable;
 
 
+/** Represents S/Q pairs. They are immutable! */
 public class SQ implements Serializable {
 
+    public interface Factory {
+        SQ createSQ(double s, double q);
+    }
+
+    public static final Factory SQ_FACTORY = new Factory() {
+        @Override
+        public SQ createSQ(double s, double q) {
+            return new SQ(s, q);
+        }
+    };
+
+    public interface View {
+        double getS(SQ sq);
+        double getQ(SQ sq);
+    }
+
+    public static final View SQ_VIEW = new View() {
+        @Override
+        public double getS(SQ sq) {
+            return sq.getS();
+        }
+
+        @Override
+        public double getQ(SQ sq) {
+            return sq.getQ();
+        }
+    };
+
     protected double s;
     protected double q;
 
@@ -29,19 +58,10 @@
         return s;
     }
 
-    public void setS(double s) {
-        this.s = s;
-    }
-
-
     public double getQ() {
         return q;
     }
 
-    public void setQ(double q) {
-        this.q = q;
-    }
-
     public boolean isValid() {
         return !Double.isNaN(s) && !Double.isNaN(q);
     }