diff --git a/src/main/java/org/gcube/informationsystem/utils/knowledge/Tree.java b/src/main/java/org/gcube/informationsystem/utils/knowledge/Tree.java
index d89e045..40ca8be 100644
--- a/src/main/java/org/gcube/informationsystem/utils/knowledge/Tree.java
+++ b/src/main/java/org/gcube/informationsystem/utils/knowledge/Tree.java
@@ -28,7 +28,7 @@ public class Tree {
 		this.allowMultipleInheritance = allowMultipleInheritance;
 	}
 	
-	public void createUsageKnowledge(Type type) {
+	protected void createUsageKnowledge(Type type) {
 		if(type.getAccessType() != AccessType.RESOURCE) {
 			return;
 		}