diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/er/entity/EntityManagement.java b/src/main/java/org/gcube/informationsystem/resourceregistry/er/entity/EntityManagement.java
index 2f3e383..e2a65d6 100644
--- a/src/main/java/org/gcube/informationsystem/resourceregistry/er/entity/EntityManagement.java
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/er/entity/EntityManagement.java
@@ -62,6 +62,11 @@ public abstract class EntityManagement<E extends Entity> extends
 	}
 	
 	@SuppressWarnings("rawtypes")
+	/*
+	 * It works perfectly in case of any kind of update.
+	 * In case of use from create the cache does not work by using the ID because until commit the edge has a fake id
+	 * starting with - (minus) sign. This not imply any collateral effect but a better solution is a desiderata. 
+	 */
 	protected RelationManagement getRelationManagement(Edge edge) throws ResourceRegistryException {
 		String id = edge.getId().toString();
 		RelationManagement relationManagement = relationManagements.get(id);
@@ -75,7 +80,7 @@ public abstract class EntityManagement<E extends Entity> extends
 	protected void addToRelationManagement(@SuppressWarnings("rawtypes") RelationManagement relationManagement) throws ResourceRegistryException {
 		Element elem = relationManagement.getElement();
 		String id = elem.getId().toString();
-		if(relationManagements.get(id)!=relationManagement) {
+		if(relationManagements.get(id)!=null && relationManagements.get(id)!=relationManagement) {
 			StringBuilder errorMessage = new StringBuilder();
 			errorMessage.append("Two different instance of ");
 			errorMessage.append(relationManagement.getClass().getSimpleName());
diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/er/entity/ResourceManagement.java b/src/main/java/org/gcube/informationsystem/resourceregistry/er/entity/ResourceManagement.java
index 6a98faf..df9428a 100644
--- a/src/main/java/org/gcube/informationsystem/resourceregistry/er/entity/ResourceManagement.java
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/er/entity/ResourceManagement.java
@@ -87,9 +87,11 @@ public class ResourceManagement extends EntityManagement<Resource> {
 			
 			@SuppressWarnings("rawtypes")
 			RelationManagement relationManagement = getRelationManagement(edge);
-			if(relationManagement.getSourceEntityManagement()==null) {
+			if(relationManagement.giveMeSourceEntityManagementAsIs()==null) {
 				relationManagement.setSourceEntityManagement(this);
-			}else if(relationManagement.getSourceEntityManagement()!=null) {
+			}
+			
+			if(relationManagement.giveMeSourceEntityManagementAsIs()!=this) {
 				StringBuilder errorMessage = new StringBuilder();
 				errorMessage.append("SourceEntityManagement for ");
 				errorMessage.append(relationManagement.getClass().getSimpleName());
diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/er/relation/RelationManagement.java b/src/main/java/org/gcube/informationsystem/resourceregistry/er/relation/RelationManagement.java
index b29576f..5a6f001 100644
--- a/src/main/java/org/gcube/informationsystem/resourceregistry/er/relation/RelationManagement.java
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/er/relation/RelationManagement.java
@@ -52,8 +52,8 @@ public abstract class RelationManagement<R extends Relation, S extends EntityMan
 
 	protected final Class<? extends Entity> targetEntityClass;
 
-	private S sourceEntityManagement;
-	private T targetEntityManagement;
+	protected S sourceEntityManagement;
+	protected T targetEntityManagement;
 
 	protected RelationManagement(AccessType accessType) {
 		super(accessType);
@@ -90,6 +90,14 @@ public abstract class RelationManagement<R extends Relation, S extends EntityMan
 		this.orientGraph = orientGraph;
 	}
 
+	/*
+	 * Needed for ResourceManagement.serializeAsJson() function to check that sourceEntityManagement is the same of
+	 * the instance is creating this RelationManagement. TODO Look for a workaround
+	 */
+	public S giveMeSourceEntityManagementAsIs() throws ResourceRegistryException {
+		return sourceEntityManagement;
+	}
+	
 	@SuppressWarnings("unchecked")
 	public S getSourceEntityManagement() throws ResourceRegistryException {
 		if (sourceEntityManagement == null) {