diff --git a/src/main/java/li/strolch/model/GroupedParameterizedElement.java b/src/main/java/li/strolch/model/GroupedParameterizedElement.java
index aef6552fd..0bf081c05 100644
--- a/src/main/java/li/strolch/model/GroupedParameterizedElement.java
+++ b/src/main/java/li/strolch/model/GroupedParameterizedElement.java
@@ -49,7 +49,7 @@ public abstract class GroupedParameterizedElement extends AbstractStrolchElement
 
 	/**
 	 * Default Constructor
-	 *
+	 * 
 	 * @param id
 	 * @param name
 	 * @param type
@@ -66,8 +66,9 @@ public abstract class GroupedParameterizedElement extends AbstractStrolchElement
 
 	/**
 	 * Sets the type of this {@link GroupedParameterizedElement}
-	 *
-	 * @param type the type to set
+	 * 
+	 * @param type
+	 *            the type to set
 	 */
 	public void setType(String type) {
 		if (StringHelper.isEmpty(type)) {
@@ -82,10 +83,12 @@ public abstract class GroupedParameterizedElement extends AbstractStrolchElement
 	/**
 	 * Returns the {@link Parameter} with the given key from the {@link ParameterBag} with the given bagKey, or null if
 	 * the {@link Parameter} or the {@link ParameterBag} does not exist
-	 *
-	 * @param bagKey the key of the {@link ParameterBag} from which the {@link Parameter} is to be returned
-	 * @param paramKey the key of the {@link Parameter} which is to be returned
-	 *
+	 * 
+	 * @param bagKey
+	 *            the key of the {@link ParameterBag} from which the {@link Parameter} is to be returned
+	 * @param paramKey
+	 *            the key of the {@link Parameter} which is to be returned
+	 * 
 	 * @return the found {@link Parameter} or null if it was not found
 	 */
 	public <T> T getParameter(String bagKey, String paramKey) {
@@ -102,11 +105,14 @@ public abstract class GroupedParameterizedElement extends AbstractStrolchElement
 
 	/**
 	 * Adds a new {@link Parameter} to the {@link ParameterBag} with the given key
-	 *
-	 * @param bagKey the key of the {@link ParameterBag} to which the {@link Parameter} should be added
-	 * @param parameter the {@link Parameter} to be added to the {@link ParameterBag}
-	 *
-	 * @throws StrolchException if the {@link ParameterBag} does not exist
+	 * 
+	 * @param bagKey
+	 *            the key of the {@link ParameterBag} to which the {@link Parameter} should be added
+	 * @param parameter
+	 *            the {@link Parameter} to be added to the {@link ParameterBag}
+	 * 
+	 * @throws StrolchException
+	 *             if the {@link ParameterBag} does not exist
 	 */
 	public void addParameter(String bagKey, Parameter<?> parameter) throws StrolchException {
 		if (this.parameterBagMap == null) {
@@ -124,10 +130,12 @@ public abstract class GroupedParameterizedElement extends AbstractStrolchElement
 
 	/**
 	 * Removes the {@link Parameter} with the given paramKey from the {@link ParameterBag} with the given bagKey
-	 *
-	 * @param bagKey the key of the {@link ParameterBag} from which the {@link Parameter} is to be removed
-	 * @param paramKey the key of the {@link Parameter} which is to be removed
-	 *
+	 * 
+	 * @param bagKey
+	 *            the key of the {@link ParameterBag} from which the {@link Parameter} is to be removed
+	 * @param paramKey
+	 *            the key of the {@link Parameter} which is to be removed
+	 * 
 	 * @return the removed {@link Parameter} or null if it did not exist
 	 */
 	public <T> Parameter<T> removeParameter(String bagKey, String paramKey) {
@@ -144,9 +152,10 @@ public abstract class GroupedParameterizedElement extends AbstractStrolchElement
 
 	/**
 	 * Returns the {@link ParameterBag} with the given key, or null if it does not exist
-	 *
-	 * @param key the key of the {@link ParameterBag} to return
-	 *
+	 * 
+	 * @param key
+	 *            the key of the {@link ParameterBag} to return
+	 * 
 	 * @return the {@link ParameterBag} with the given key, or null if it does not exist
 	 */
 	public ParameterBag getParameterBag(String key) {
@@ -158,22 +167,29 @@ public abstract class GroupedParameterizedElement extends AbstractStrolchElement
 
 	/**
 	 * Adds the given {@link ParameterBag} to this {@link GroupedParameterizedElement}
-	 *
-	 * @param bag the {@link ParameterBag} to add
+	 * 
+	 * @param bag
+	 *            the {@link ParameterBag} to add
 	 */
 	public void addParameterBag(ParameterBag bag) {
 		if (this.parameterBagMap == null) {
 			this.parameterBagMap = new HashMap<String, ParameterBag>();
 		}
+
+		if (this.parameterBagMap.containsKey(bag.getId())) {
+			String msg = "A ParameterBag already exists with id {0} on {1}";
+			throw new StrolchException(MessageFormat.format(msg, bag.getId(), getLocator()));
+		}
 		this.parameterBagMap.put(bag.getId(), bag);
 		bag.setParent(this);
 	}
 
 	/**
 	 * Removes the {@link ParameterBag} with the given key
-	 *
-	 * @param key the key of the {@link ParameterBag} to remove
-	 *
+	 * 
+	 * @param key
+	 *            the key of the {@link ParameterBag} to remove
+	 * 
 	 * @return the removed {@link ParameterBag}, or null if it does not exist
 	 */
 	public ParameterBag removeParameterBag(String key) {
@@ -185,7 +201,7 @@ public abstract class GroupedParameterizedElement extends AbstractStrolchElement
 
 	/**
 	 * Returns true if this {@link GroupedParameterizedElement} has any {@link ParameterBag ParameterBag}
-	 *
+	 * 
 	 * @return true if this {@link GroupedParameterizedElement} has any {@link ParameterBag ParameterBag}
 	 */
 	public boolean hasParameterBags() {
@@ -194,8 +210,9 @@ public abstract class GroupedParameterizedElement extends AbstractStrolchElement
 
 	/**
 	 * Returns true if the {@link ParameterBag} with the given key exists on this {@link GroupedParameterizedElement}.
-	 *
-	 * @param bagKey the key of the {@link ParameterBag} which is to be checked for existence
+	 * 
+	 * @param bagKey
+	 *            the key of the {@link ParameterBag} which is to be checked for existence
 	 * @return true if the {@link ParameterBag} with the given key exists on this {@link GroupedParameterizedElement}.
 	 */
 	public boolean hasParameterBag(String bagKey) {
@@ -205,13 +222,15 @@ public abstract class GroupedParameterizedElement extends AbstractStrolchElement
 	/**
 	 * Returns true if the {@link Parameter} with the given paramKey exists on the {@link ParameterBag} with the given
 	 * bagKey
-	 *
-	 * @param bagKey the key of the {@link ParameterBag} on which to find the {@link Parameter}
-	 * @param paramKey the key of the {@link Parameter} to be found
-	 *
+	 * 
+	 * @param bagKey
+	 *            the key of the {@link ParameterBag} on which to find the {@link Parameter}
+	 * @param paramKey
+	 *            the key of the {@link Parameter} to be found
+	 * 
 	 * @return true if the {@link Parameter} with the given paramKey exists on the {@link ParameterBag} with the given
-	 * bagKey. False is returned if the {@link ParameterBag} does not exist, or the {@link Parameter} does not exist on
-	 * the {@link ParameterBag}
+	 *         bagKey. False is returned if the {@link ParameterBag} does not exist, or the {@link Parameter} does not
+	 *         exist on the {@link ParameterBag}
 	 */
 	public boolean hasParameter(String bagKey, String paramKey) {
 		if (this.parameterBagMap == null) {
@@ -227,7 +246,7 @@ public abstract class GroupedParameterizedElement extends AbstractStrolchElement
 
 	/**
 	 * Returns the {@link Set} of keys for the {@link ParameterBag}s on this {@link GroupedParameterizedElement}
-	 *
+	 * 
 	 * @return the {@link Set} of keys for the {@link ParameterBag}s on this {@link GroupedParameterizedElement}
 	 */
 	public Set<String> getParameterBagKeySet() {
@@ -265,7 +284,7 @@ public abstract class GroupedParameterizedElement extends AbstractStrolchElement
 
 	/**
 	 * Fills {@link GroupedParameterizedElement} properties of this clone
-	 *
+	 * 
 	 * @param clone
 	 */
 	protected void fillClone(GroupedParameterizedElement clone) {
diff --git a/src/main/java/li/strolch/model/ParameterizedElement.java b/src/main/java/li/strolch/model/ParameterizedElement.java
index 14299ea50..6a8e2b9cd 100644
--- a/src/main/java/li/strolch/model/ParameterizedElement.java
+++ b/src/main/java/li/strolch/model/ParameterizedElement.java
@@ -16,6 +16,7 @@
 package li.strolch.model;
 
 import ch.eitchnet.utils.dbc.DBC;
+
 import java.text.MessageFormat;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -61,7 +62,7 @@ public abstract class ParameterizedElement extends AbstractStrolchElement {
 
 	/**
 	 * Default Constructor
-	 *
+	 * 
 	 * @param id
 	 * @param name
 	 * @param type
@@ -79,8 +80,9 @@ public abstract class ParameterizedElement extends AbstractStrolchElement {
 
 	/**
 	 * Sets the type of this {@link ParameterizedElement}
-	 *
-	 * @param type the type to set
+	 * 
+	 * @param type
+	 *            the type to set
 	 */
 	public void setType(String type) {
 		if (StringHelper.isEmpty(type)) {
@@ -94,9 +96,10 @@ public abstract class ParameterizedElement extends AbstractStrolchElement {
 
 	/**
 	 * Returns the {@link Parameter} with the given id, or null if it does not exist
-	 *
-	 * @param key the id of the parameter to return
-	 *
+	 * 
+	 * @param key
+	 *            the id of the parameter to return
+	 * 
 	 * @return the {@link Parameter} with the given id, or null if it does not exist
 	 */
 	@SuppressWarnings("unchecked")
@@ -109,22 +112,29 @@ public abstract class ParameterizedElement extends AbstractStrolchElement {
 
 	/**
 	 * Adds the given {@link Parameter} to the {@link ParameterizedElement}
-	 *
-	 * @param parameter the {@link Parameter} to add
+	 * 
+	 * @param parameter
+	 *            the {@link Parameter} to add
 	 */
 	public void addParameter(Parameter<?> parameter) {
 		if (this.parameterMap == null) {
 			this.parameterMap = new HashMap<String, Parameter<?>>();
 		}
+
+		if (this.parameterMap.containsKey(parameter.getId())) {
+			String msg = "A Parameter already exists with id {0} on {1}";
+			throw new StrolchException(MessageFormat.format(msg, parameter.getId(), getLocator()));
+		}
 		this.parameterMap.put(parameter.getId(), parameter);
 		parameter.setParent(this);
 	}
 
 	/**
 	 * Removes the {@link Parameter} with the given key
-	 *
-	 * @param key the key of the {@link Parameter} to remove
-	 *
+	 * 
+	 * @param key
+	 *            the key of the {@link Parameter} to remove
+	 * 
 	 * @return the removed {@link Parameter}, or null if it does not exist
 	 */
 	@SuppressWarnings("unchecked")
@@ -137,7 +147,7 @@ public abstract class ParameterizedElement extends AbstractStrolchElement {
 
 	/**
 	 * Returns a list of all the {@link Parameter}s in this {@link ParameterizedElement}
-	 *
+	 * 
 	 * @return a list of all the {@link Parameter}s in this {@link ParameterizedElement}
 	 */
 	public List<Parameter<?>> getParameters() {
@@ -149,7 +159,7 @@ public abstract class ParameterizedElement extends AbstractStrolchElement {
 
 	/**
 	 * Returns true, if the this {@link ParameterizedElement} has any {@link Parameter Parameters}, false otherwise
-	 *
+	 * 
 	 * @return true, if the this {@link ParameterizedElement} has any {@link Parameter Parameters}, false otherwise
 	 */
 	public boolean hasParameters() {
@@ -158,9 +168,10 @@ public abstract class ParameterizedElement extends AbstractStrolchElement {
 
 	/**
 	 * Returns true, if the {@link Parameter} exists with the given key, false otherwise
-	 *
-	 * @param key the key of the {@link Parameter} to check for
-	 *
+	 * 
+	 * @param key
+	 *            the key of the {@link Parameter} to check for
+	 * 
 	 * @return true, if the {@link Parameter} exists with the given key, false otherwise
 	 */
 	public boolean hasParameter(String key) {
@@ -172,7 +183,7 @@ public abstract class ParameterizedElement extends AbstractStrolchElement {
 
 	/**
 	 * Returns a {@link Set} of all the {@link Parameter} keys in this {@link ParameterizedElement}
-	 *
+	 * 
 	 * @return a {@link Set} of all the {@link Parameter} keys in this {@link ParameterizedElement}
 	 */
 	public Set<String> getParameterKeySet() {
@@ -269,8 +280,9 @@ public abstract class ParameterizedElement extends AbstractStrolchElement {
 
 	/**
 	 * Set the parent for this {@link ParameterizedElement}
-	 *
-	 * @param parent the parent to set
+	 * 
+	 * @param parent
+	 *            the parent to set
 	 */
 	public void setParent(GroupedParameterizedElement parent) {
 		this.parent = parent;
diff --git a/src/main/java/li/strolch/model/parameter/Parameter.java b/src/main/java/li/strolch/model/parameter/Parameter.java
index e9c46140e..3eae2ef9f 100644
--- a/src/main/java/li/strolch/model/parameter/Parameter.java
+++ b/src/main/java/li/strolch/model/parameter/Parameter.java
@@ -15,15 +15,13 @@
  */
 package li.strolch.model.parameter;
 
-import li.strolch.model.Order;
 import li.strolch.model.ParameterizedElement;
-import li.strolch.model.Resource;
 import li.strolch.model.StrolchElement;
 import li.strolch.model.visitor.ParameterVisitor;
 
 /**
  * @author Robert von Burg <eitch@eitchnet.ch>
- *
+ * 
  */
 public interface Parameter<T> extends StrolchElement {
 
@@ -37,84 +35,73 @@ public interface Parameter<T> extends StrolchElement {
 	 */
 	public static final String UOM_NONE = "None"; //$NON-NLS-1$
 
-	/**
-	 * This interpretation value indicates that the value of the {@link Parameter} should be understood as a reference
-	 * to a {@link Resource}
-	 */
-	public static final String INTERPRETATION_RESOURCE_REF = "Resource-Reference"; //$NON-NLS-1$
-
-	/**
-	 * This interpretation value indicates that the value of the {@link Parameter} should be understood as a reference
-	 * to a {@link Order}
-	 */
-	public static final String INTERPRETATION_ORDER_REF = "Order-Reference"; //$NON-NLS-1$
-
 	/**
 	 * the value of the parameter as string
-	 *
+	 * 
 	 * @return String
 	 */
 	public String getValueAsString();
 
 	/**
 	 * the value of the parameter
-	 *
+	 * 
 	 * @return
 	 */
 	public T getValue();
 
 	/**
 	 * the value of the parameter
-	 *
+	 * 
 	 * @param value
 	 */
 	public void setValue(T value);
 
 	/**
 	 * get the hidden attribute
-	 *
+	 * 
 	 * @return
 	 */
 	public boolean isHidden();
 
 	/**
 	 * set the hidden attribute
-	 *
+	 * 
 	 * @param hidden
 	 */
 	public void setHidden(boolean hidden);
 
 	/**
 	 * Get the UOM of this {@link Parameter}
-	 *
+	 * 
 	 * @return
 	 */
 	public String getUom();
 
 	/**
 	 * Set the UOM of this {@link Parameter}
-	 *
+	 * 
 	 * @param uom
 	 */
 	public void setUom(String uom);
 
 	/**
 	 * Returns the index of this {@link Parameter}. This can be used to sort the parameters in a UI
-	 *
+	 * 
 	 * @return the index of this {@link Parameter}. This can be used to sort the parameters in a UI
 	 */
 	public int getIndex();
 
 	/**
 	 * Set the index of this {@link Parameter}. This can be used to sort the parameters in a UI
-	 *
-	 * @param index the index to set
+	 * 
+	 * @param index
+	 *            the index to set
 	 */
 	public void setIndex(int index);
 
 	/**
 	 * The {@link ParameterizedElement} parent to which this {@link Parameter} belongs
-	 *
+	 * 
 	 * @return
 	 */
 	public ParameterizedElement getParent();
@@ -132,7 +119,7 @@ public interface Parameter<T> extends StrolchElement {
 	 * <li>{@link Parameter#INTERPRETATION_ORDER_REF}</li>
 	 * <li>{@link Parameter#INTERPRETATION_RESOURCE_REF}</li>
 	 * </ul>
-	 *
+	 * 
 	 * @return string value
 	 */
 	public String getInterpretation();
@@ -145,7 +132,7 @@ public interface Parameter<T> extends StrolchElement {
 	 * <li>{@link Parameter#INTERPRETATION_ORDER_REF}</li>
 	 * <li>{@link Parameter#INTERPRETATION_RESOURCE_REF}</li>
 	 * </ul>
-	 *
+	 * 
 	 * @param interpretation
 	 */
 	public void setInterpretation(String interpretation);