diff --git a/src/main/java/org/gcube/informationsystem/model/reference/ModelElement.java b/src/main/java/org/gcube/informationsystem/model/reference/ModelElement.java
new file mode 100644
index 0000000..9f34688
--- /dev/null
+++ b/src/main/java/org/gcube/informationsystem/model/reference/ModelElement.java
@@ -0,0 +1,13 @@
+package org.gcube.informationsystem.model.reference;
+
+import org.gcube.informationsystem.base.reference.IdentifiableElement;
+
+/**
+ * This interfaces is an helper to identify elements of the model
+ * i.e. REsource, Facet, IsRelatedTo, ConsistsOf
+ * 
+ * @author Luca Frosini (ISTI - CNR)
+ */
+public interface ModelElement extends IdentifiableElement {
+
+}
diff --git a/src/main/java/org/gcube/informationsystem/model/reference/entities/Entity.java b/src/main/java/org/gcube/informationsystem/model/reference/entities/Entity.java
index 60b5063..ab4e447 100644
--- a/src/main/java/org/gcube/informationsystem/model/reference/entities/Entity.java
+++ b/src/main/java/org/gcube/informationsystem/model/reference/entities/Entity.java
@@ -4,6 +4,7 @@
 package org.gcube.informationsystem.model.reference.entities;
 
 import org.gcube.informationsystem.base.reference.entities.EntityElement;
+import org.gcube.informationsystem.model.reference.ModelElement;
 import org.gcube.informationsystem.types.annotations.Abstract;
 import org.gcube.informationsystem.types.reference.Change;
 import org.gcube.informationsystem.types.reference.TypeMetadata;
@@ -18,7 +19,7 @@ import org.gcube.informationsystem.utils.TypeVersion;
 //@JsonDeserialize(as=EntityImpl.class) Do not uncomment to manage subclasses
 @TypeMetadata(name = Entity.NAME, description = "This is the base class for Entities", version = TypeVersion.MINIMAL_VERSION_STRING)
 @Change(version = TypeVersion.MINIMAL_VERSION_STRING, description = TypeVersion.MINIMAL_VERSION_DESCRIPTION)
-public interface Entity extends EntityElement {
+public interface Entity extends EntityElement, ModelElement {
 	
 	public static final String NAME = "Entity"; //Entity.class.getSimpleName();
 	
diff --git a/src/main/java/org/gcube/informationsystem/model/reference/relations/Relation.java b/src/main/java/org/gcube/informationsystem/model/reference/relations/Relation.java
index bbb50bf..58b37e5 100644
--- a/src/main/java/org/gcube/informationsystem/model/reference/relations/Relation.java
+++ b/src/main/java/org/gcube/informationsystem/model/reference/relations/Relation.java
@@ -13,6 +13,7 @@ import org.gcube.com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import org.gcube.com.fasterxml.jackson.databind.annotation.JsonSerialize;
 import org.gcube.informationsystem.base.reference.SchemaMixedElement;
 import org.gcube.informationsystem.base.reference.relations.RelationElement;
+import org.gcube.informationsystem.model.reference.ModelElement;
 import org.gcube.informationsystem.model.reference.entities.Entity;
 import org.gcube.informationsystem.model.reference.entities.Resource;
 import org.gcube.informationsystem.model.reference.properties.PropagationConstraint;
@@ -32,7 +33,7 @@ import org.gcube.informationsystem.utils.TypeVersion;
 // @JsonDeserialize(as=RelationImpl.class) Do not uncomment to manage subclasses
 @TypeMetadata(name = Relation.NAME, description = "This is the base class for Relations", version = TypeVersion.MINIMAL_VERSION_STRING)
 @Change(version = TypeVersion.MINIMAL_VERSION_STRING, description = TypeVersion.MINIMAL_VERSION_DESCRIPTION)
-public interface Relation<S extends Resource, T extends Entity> extends RelationElement<S,T>, SchemaMixedElement {
+public interface Relation<S extends Resource, T extends Entity> extends RelationElement<S,T>, SchemaMixedElement, ModelElement {
 	
 	public static final String NAME = "Relation"; //Relation.class.getSimpleName();