diff --git a/src/main/java/org/gcube/informationsystem/discovery/knowledge/ModelKnowledge.java b/src/main/java/org/gcube/informationsystem/discovery/knowledge/ModelKnowledge.java
index eb5a6e1..2729110 100644
--- a/src/main/java/org/gcube/informationsystem/discovery/knowledge/ModelKnowledge.java
+++ b/src/main/java/org/gcube/informationsystem/discovery/knowledge/ModelKnowledge.java
@@ -6,7 +6,6 @@ import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
-import java.util.ServiceLoader;
 import java.util.Set;
 
 import org.gcube.informationsystem.base.reference.AccessType;
@@ -25,20 +24,6 @@ public class ModelKnowledge {
 	
 	private static final Logger logger = LoggerFactory.getLogger(ModelKnowledge.class);
 	
-	private static ModelKnowledge modelKnowledge;
-	
-	public static ModelKnowledge getGlobalModelKnowledgeInstance() {
-		if(modelKnowledge==null) {
-			modelKnowledge = new ModelKnowledge();
-			ServiceLoader<? extends RegistrationProvider> registrationProviders = ServiceLoader
-					.load(RegistrationProvider.class);
-			for(RegistrationProvider rp : registrationProviders) {
-				modelKnowledge.addRegistrationProvider(rp);
-			}
-		}
-		return modelKnowledge;
-	}
-	
 	protected boolean created;
 	
 	protected Map<AccessType,UsageKnowledge> usageKnowledges;
diff --git a/src/main/java/org/gcube/informationsystem/serialization/ElementMapper.java b/src/main/java/org/gcube/informationsystem/serialization/ElementMapper.java
index d6f7c8d..2c34612 100644
--- a/src/main/java/org/gcube/informationsystem/serialization/ElementMapper.java
+++ b/src/main/java/org/gcube/informationsystem/serialization/ElementMapper.java
@@ -12,6 +12,7 @@ import java.util.Iterator;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.ServiceLoader;
 import java.util.Set;
 
 import org.gcube.com.fasterxml.jackson.core.JsonGenerationException;
@@ -30,6 +31,7 @@ import org.gcube.com.fasterxml.jackson.databind.node.TextNode;
 import org.gcube.informationsystem.base.reference.AccessType;
 import org.gcube.informationsystem.base.reference.Element;
 import org.gcube.informationsystem.discovery.Discovery;
+import org.gcube.informationsystem.discovery.RegistrationProvider;
 import org.gcube.informationsystem.discovery.knowledge.ModelKnowledge;
 import org.gcube.informationsystem.types.TypeMapper;
 import org.gcube.informationsystem.types.reference.Type;
@@ -47,7 +49,21 @@ public abstract class ElementMapper {
 	protected static final ObjectMapper mapper;
 	
 	protected static final Map<String, Class<? extends Element>> knownTypes;
-//	
+	
+	private static ModelKnowledge modelKnowledge;
+	
+	public static ModelKnowledge getGlobalModelKnowledgeInstance() {
+		if(modelKnowledge==null) {
+			modelKnowledge = new ModelKnowledge();
+			ServiceLoader<? extends RegistrationProvider> registrationProviders = ServiceLoader
+					.load(RegistrationProvider.class);
+			for(RegistrationProvider rp : registrationProviders) {
+				modelKnowledge.addRegistrationProvider(rp);
+			}
+		}
+		return modelKnowledge;
+	}
+	
 	/**
 	 * @return the ObjectMapper
 	 */
@@ -107,7 +123,7 @@ public abstract class ElementMapper {
 		}
 		
 		try {
-			ModelKnowledge.getGlobalModelKnowledgeInstance().createKnowledge();
+			ElementMapper.getGlobalModelKnowledgeInstance().createKnowledge();
 		}catch (Exception e) {
 			throw new RuntimeException(e);
 		}
diff --git a/src/test/java/org/gcube/informationsystem/discovery/DiscoveryTest.java b/src/test/java/org/gcube/informationsystem/discovery/DiscoveryTest.java
index 2e1fd96..0113fb0 100644
--- a/src/test/java/org/gcube/informationsystem/discovery/DiscoveryTest.java
+++ b/src/test/java/org/gcube/informationsystem/discovery/DiscoveryTest.java
@@ -5,6 +5,7 @@ import java.util.Map;
 import org.gcube.informationsystem.base.reference.AccessType;
 import org.gcube.informationsystem.base.reference.Element;
 import org.gcube.informationsystem.discovery.knowledge.ModelKnowledge;
+import org.gcube.informationsystem.serialization.ElementMapper;
 import org.gcube.informationsystem.tree.Tree;
 import org.gcube.informationsystem.types.TypeMapper;
 import org.gcube.informationsystem.types.reference.Type;
@@ -25,18 +26,13 @@ public class DiscoveryTest {
 	
 	@Test
 	public void testDiscovery() throws Exception {
-		ModelKnowledge modelKnowledge = ModelKnowledge.getGlobalModelKnowledgeInstance();
+		ModelKnowledge modelKnowledge = ElementMapper.getGlobalModelKnowledgeInstance();
 		modelKnowledge.createKnowledge();
 		
 		AccessType[] accessTypes = AccessType.getModelTypes();
 		for(AccessType accessType : accessTypes) {
-			
 			Tree<Class<Element>> classesTree = modelKnowledge.getClassesTree(accessType);
 			logger.info("Classes tree for {} is\n{}", accessType.getName(), classesTree.toString());
-			
-//			Tree<Type> typesTree = modelKnowledge.getTypesTree(accessType);
-//			logger.info("Types tree for {} is\n{}", accessType.getName(), typesTree.toString());
-			
 		}
 	}