diff --git a/src/main/java/org/gcube/informationsystem/discovery/ISModelRegistrationProvider.java b/src/main/java/org/gcube/informationsystem/discovery/ISModelRegistrationProvider.java
index 7a1050d..c2d6400 100644
--- a/src/main/java/org/gcube/informationsystem/discovery/ISModelRegistrationProvider.java
+++ b/src/main/java/org/gcube/informationsystem/discovery/ISModelRegistrationProvider.java
@@ -15,7 +15,7 @@ public class ISModelRegistrationProvider implements RegistrationProvider {
 	
 	static {
 		packages = new HashSet<>();
-		for(AccessType accessType : RegistrationProvider.getAccessTypes()) {
+		for(AccessType accessType : AccessType.getModelTypes()) {
 			Class<Element> clz = accessType.getTypeClass();
 			packages.add(clz.getPackage());
 		}
diff --git a/src/main/java/org/gcube/informationsystem/discovery/RegistrationProvider.java b/src/main/java/org/gcube/informationsystem/discovery/RegistrationProvider.java
index 15fa77b..41cb96d 100644
--- a/src/main/java/org/gcube/informationsystem/discovery/RegistrationProvider.java
+++ b/src/main/java/org/gcube/informationsystem/discovery/RegistrationProvider.java
@@ -1,10 +1,6 @@
 package org.gcube.informationsystem.discovery;
 
 import java.util.Collection;
-import java.util.LinkedHashSet;
-import java.util.Set;
-
-import org.gcube.informationsystem.base.reference.AccessType;
 
 /**
  * Any model requires to register the defined types.
@@ -28,14 +24,4 @@ public interface RegistrationProvider {
 	 */
 	public Collection<Package> getPackagesToRegister();
 	
-
-	public static Set<AccessType> getAccessTypes() {
-		Set<AccessType> accessTypes = new LinkedHashSet<>();
-		accessTypes.add(AccessType.PROPERTY);
-		accessTypes.add(AccessType.RESOURCE);
-		accessTypes.add(AccessType.FACET);
-		accessTypes.add(AccessType.IS_RELATED_TO);
-		accessTypes.add(AccessType.CONSISTS_OF);
-		return accessTypes;
-	}
 }
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 88696a2..fe63c35 100644
--- a/src/main/java/org/gcube/informationsystem/discovery/knowledge/ModelKnowledge.java
+++ b/src/main/java/org/gcube/informationsystem/discovery/knowledge/ModelKnowledge.java
@@ -1,7 +1,9 @@
 package org.gcube.informationsystem.discovery.knowledge;
 
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.ServiceLoader;
 import java.util.Set;
 
 import org.gcube.informationsystem.base.reference.AccessType;
@@ -17,20 +19,25 @@ import org.gcube.informationsystem.tree.Tree;
  */
 public class ModelKnowledge {
 
-	protected RegistrationProvider registrationProvider;
-	
 	protected Map<AccessType, Tree<Class<Element>>> trees;
+
 	protected Map<AccessType, Discovery<? extends Element>> discoveries;
 	
-	public ModelKnowledge(RegistrationProvider registrationProvider) {
-		this.registrationProvider = registrationProvider;
+	public ModelKnowledge() {
 		this.trees = new HashMap<>();
 		this.discoveries = new HashMap<>();
 	}
 	
 	public void createKnowledge() throws Exception {
 		
-		Set<AccessType> modelTypes = RegistrationProvider.getAccessTypes();
+		AccessType[] modelTypes = AccessType.getModelTypes();
+		
+		Set<Package> allPackages = new HashSet<>();
+		ServiceLoader<? extends RegistrationProvider> registrationProviders = ServiceLoader
+				.load(RegistrationProvider.class);
+		for(RegistrationProvider rp : registrationProviders) {
+			allPackages.addAll(rp.getPackagesToRegister());
+		}
 		
 		for(AccessType accessType : modelTypes) {
 			Class<Element> clz = accessType.getTypeClass();
@@ -41,22 +48,18 @@ public class ModelKnowledge {
 			
 			Discovery<? extends Element> discovery = new Discovery<>(clz);
 			discoveries.put(accessType, discovery);
-			
-			discovery.addPackages(registrationProvider.getPackagesToRegister());
+			discovery.addPackages(allPackages);
 			discovery.addDiscoveredElementActions(new ElementMappingAction());
 			discovery.addDiscoveredElementActions(aetta);
 			
 			discovery.discover();
+			
 		}
 		
 	}
 	
-	public Map<AccessType, Tree<Class<Element>>> getTrees() {
-		return trees;
+	public Tree<Class<Element>> getTree(AccessType accessType) {
+		return trees.get(accessType);
 	}
 
-	public void setTrees(Map<AccessType, Tree<Class<Element>>> trees) {
-		this.trees = trees;
-	}
-	
 }