diff --git a/CHANGELOG.md b/CHANGELOG.md
index 80bdd03..86746c7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,13 +4,16 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [v4.1.0-SNAPSHOT] 
 
-- Prepared Query has been fixed to properly consider polymorphic parameter and provided constraint [#20298]
-- Added type update but the API is not exposed via REST [#20316]
-- Generalised the definition of the type of a property [#20516]
-- Add/Remove to/from Context return the list of affected instances and not just success or failure code [#20555]
-- Added the possibility to have a dry run Add/Remove to/from Context [#20530]
+- Relation source-target instace types are validated against Relation schema [#7355]
+- The instances are validated with the defined schema [#18216]
+- Added Types Cache [#18496]
+- Superclasses in instances are ordered and does not include internal basic types [#20517]
 - Redesigned Sharing REST collection [#20530][#20555] 
-
+- Added the possibility to have a dry run Add/Remove to/from Context [#20530]
+- Add/Remove to/from Context return the list of affected instances and not just success or failure code [#20555]
+- Generalised the definition of the type of a property [#20516]
+- Added type update but the API is not exposed via REST [#20316]
+- Prepared Query has been fixed to properly consider polymorphic parameter and provided constraint [#20298]
 
 ## [v4.0.0] 
 
diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/contexts/relations/IsParentOfManagement.java b/src/main/java/org/gcube/informationsystem/resourceregistry/contexts/relations/IsParentOfManagement.java
index b6ee292..277a6fd 100644
--- a/src/main/java/org/gcube/informationsystem/resourceregistry/contexts/relations/IsParentOfManagement.java
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/contexts/relations/IsParentOfManagement.java
@@ -5,6 +5,7 @@ import org.gcube.com.fasterxml.jackson.databind.node.ObjectNode;
 import org.gcube.informationsystem.base.reference.AccessType;
 import org.gcube.informationsystem.context.reference.entities.Context;
 import org.gcube.informationsystem.model.reference.relations.Relation;
+import org.gcube.informationsystem.resourceregistry.api.exceptions.AvailableInAnotherContextException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.NotFoundException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.ResourceRegistryException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.relation.isparentof.IsParentOfAlreadyPresentException;
@@ -114,4 +115,10 @@ public class IsParentOfManagement extends RelationElementManagement<ContextManag
 		// Nothing to do
 	}
 
+	@Override
+	protected void checksourceAndTargetEntityCompliancy() throws NotFoundException, AvailableInAnotherContextException,
+			SchemaViolationException, ResourceRegistryException {
+		// The compliancy is ensured by the code
+	}
+
 }
diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/instances/base/ElementManagement.java b/src/main/java/org/gcube/informationsystem/resourceregistry/instances/base/ElementManagement.java
index 693db2f..e3410d1 100644
--- a/src/main/java/org/gcube/informationsystem/resourceregistry/instances/base/ElementManagement.java
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/instances/base/ElementManagement.java
@@ -46,6 +46,7 @@ import org.gcube.informationsystem.resourceregistry.utils.HeaderOrient;
 import org.gcube.informationsystem.resourceregistry.utils.HeaderUtility;
 import org.gcube.informationsystem.resourceregistry.utils.Utility;
 import org.gcube.informationsystem.types.reference.Type;
+import org.gcube.informationsystem.types.reference.entities.ResourceType;
 import org.gcube.informationsystem.types.reference.properties.PropertyDefinition;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -1093,6 +1094,20 @@ public abstract class ElementManagement<El extends OElement, T extends Type> {
 		return stringBuffer.toString();
 	}
 	
+	protected boolean typeSatified(TypesCache typesCache, String requiredType, String effectiveType) throws SchemaException, ResourceRegistryException {
+		if(requiredType.compareTo(effectiveType)==0) {
+			return true;
+		}
+		
+		@SuppressWarnings("unchecked")
+		CachedType<ResourceType> cachedType = (CachedType<ResourceType>) typesCache.getCachedType(requiredType);
+		if(cachedType.getSubTypes().contains(effectiveType)) {
+			return true;
+		}
+		
+		return false;
+	}
+	
 	/*
 	 * Get not only the properties defined in the type but also the properties 
 	 * defined in the super types 
diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/instances/base/relations/RelationElementManagement.java b/src/main/java/org/gcube/informationsystem/resourceregistry/instances/base/relations/RelationElementManagement.java
index 75ba533..66ef2f8 100644
--- a/src/main/java/org/gcube/informationsystem/resourceregistry/instances/base/relations/RelationElementManagement.java
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/instances/base/relations/RelationElementManagement.java
@@ -7,9 +7,12 @@ import org.gcube.com.fasterxml.jackson.databind.node.ObjectNode;
 import org.gcube.informationsystem.base.reference.AccessType;
 import org.gcube.informationsystem.base.reference.entities.EntityElement;
 import org.gcube.informationsystem.model.reference.relations.Relation;
+import org.gcube.informationsystem.resourceregistry.api.exceptions.AvailableInAnotherContextException;
+import org.gcube.informationsystem.resourceregistry.api.exceptions.NotFoundException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.ResourceRegistryException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.relation.RelationNotFoundException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.schema.SchemaException;
+import org.gcube.informationsystem.resourceregistry.api.exceptions.schema.SchemaViolationException;
 import org.gcube.informationsystem.resourceregistry.contexts.security.SecurityContext;
 import org.gcube.informationsystem.resourceregistry.instances.base.ElementManagement;
 import org.gcube.informationsystem.resourceregistry.instances.base.entities.EntityElementManagement;
@@ -117,6 +120,8 @@ public abstract class RelationElementManagement<SEM extends EntityElementManagem
 		return relation;
 	}
 	
+	protected abstract void checksourceAndTargetEntityCompliancy() throws NotFoundException, AvailableInAnotherContextException, SchemaViolationException, ResourceRegistryException;
+	
 	@Override
 	protected OEdge reallyCreate() throws ResourceRegistryException {
 		
@@ -164,8 +169,7 @@ public abstract class RelationElementManagement<SEM extends EntityElementManagem
 		OVertex source = (OVertex) getSourceEntityManagement().getElement();
 		OVertex target = (OVertex) getTargetEntityManagement().getElement();
 		
-		// TODO check source  and target type compatibility
-		
+		checksourceAndTargetEntityCompliancy();
 		
 		logger.trace("Going to create {} beetween {} -> {}", typeName, source.toString(), target.toString());
 
diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/entities/ResourceManagement.java b/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/entities/ResourceManagement.java
index 2619371..553d7d1 100644
--- a/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/entities/ResourceManagement.java
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/entities/ResourceManagement.java
@@ -366,20 +366,6 @@ public class ResourceManagement extends EntityManagement<Resource, ResourceType>
 		return stringBuffer.toString();
 	}
 	
-	protected boolean typeSatified(TypesCache typesCache, String requiredType, String effectiveType) throws SchemaException, ResourceRegistryException {
-		if(requiredType.compareTo(effectiveType)==0) {
-			return true;
-		}
-		
-		@SuppressWarnings("unchecked")
-		CachedType<ResourceType> cachedType = (CachedType<ResourceType>) typesCache.getCachedType(requiredType);
-		if(cachedType.getSubTypes().contains(effectiveType)) {
-			return true;
-		}
-		
-		return false;
-	}
-	
 	protected boolean constraintSatisfied(TypesCache typesCache, LinkedEntity constraint, String consistsOfType, String facetType) throws SchemaException, ResourceRegistryException {
 		String requiredSourceResourceType = constraint.getSource();
 		if(!typeSatified(typesCache, requiredSourceResourceType, typeName)) {
diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/relations/RelationManagement.java b/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/relations/RelationManagement.java
index 74cae79..e916bfc 100644
--- a/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/relations/RelationManagement.java
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/relations/RelationManagement.java
@@ -11,6 +11,7 @@ import org.gcube.com.fasterxml.jackson.databind.ObjectMapper;
 import org.gcube.com.fasterxml.jackson.databind.node.ArrayNode;
 import org.gcube.com.fasterxml.jackson.databind.node.ObjectNode;
 import org.gcube.informationsystem.base.reference.AccessType;
+import org.gcube.informationsystem.base.reference.relations.RelationElement;
 import org.gcube.informationsystem.context.reference.entities.Context;
 import org.gcube.informationsystem.model.reference.entities.Entity;
 import org.gcube.informationsystem.model.reference.entities.Resource;
@@ -23,6 +24,7 @@ import org.gcube.informationsystem.resourceregistry.api.exceptions.NotFoundExcep
 import org.gcube.informationsystem.resourceregistry.api.exceptions.ResourceRegistryException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.context.ContextException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.relation.RelationNotFoundException;
+import org.gcube.informationsystem.resourceregistry.api.exceptions.schema.SchemaViolationException;
 import org.gcube.informationsystem.resourceregistry.contexts.ContextUtility;
 import org.gcube.informationsystem.resourceregistry.contexts.security.SecurityContext;
 import org.gcube.informationsystem.resourceregistry.contexts.security.SecurityContext.PermissionMode;
@@ -33,11 +35,13 @@ import org.gcube.informationsystem.resourceregistry.instances.model.ERManagement
 import org.gcube.informationsystem.resourceregistry.instances.model.entities.EntityManagement;
 import org.gcube.informationsystem.resourceregistry.instances.model.entities.FacetManagement;
 import org.gcube.informationsystem.resourceregistry.instances.model.entities.ResourceManagement;
+import org.gcube.informationsystem.resourceregistry.types.TypesCache;
 import org.gcube.informationsystem.resourceregistry.utils.HeaderUtility;
 import org.gcube.informationsystem.resourceregistry.utils.PropagationConstraintOrient;
 import org.gcube.informationsystem.resourceregistry.utils.Utility;
 import org.gcube.informationsystem.types.reference.entities.EntityType;
 import org.gcube.informationsystem.types.reference.entities.ResourceType;
+import org.gcube.informationsystem.types.reference.relations.RelationType;
 import org.gcube.informationsystem.utils.ElementMapper;
 
 import com.orientechnologies.orient.core.db.document.ODatabaseDocument;
@@ -165,12 +169,10 @@ public abstract class RelationManagement<T extends EntityManagement<? extends En
 		return element;
 	}
 	
-	
-	
 	/*
 	 * Needed for ResourceManagement.serializeAsJson() function to check that
 	 * sourceEntityManagement is the same of the instance is creating this
-	 * RelationManagement. TODO Look for a workaround
+	 * RelationManagement.
 	 */
 	public ResourceManagement giveMeSourceEntityManagementAsIs() throws ResourceRegistryException {
 		return sourceEntityManagement;
@@ -341,6 +343,46 @@ public abstract class RelationManagement<T extends EntityManagement<? extends En
 	
 	protected abstract T newTargetEntityManagement() throws ResourceRegistryException;
 	
+	protected String getEntityTypeNotValidErrroMessage(String entityPosition, String requiredType, String effectiveType) {
+		StringBuffer stringBuffer = new StringBuffer();
+		stringBuffer.append("The ");
+		stringBuffer.append(entityPosition);
+		stringBuffer.append(" instance of the relation ");
+		stringBuffer.append(typeName);
+		stringBuffer.append(" is of type ");
+		stringBuffer.append(effectiveType);
+		stringBuffer.append(" which is not a specialisation of ");
+		stringBuffer.append(requiredType);
+		stringBuffer.append(".");
+		return stringBuffer.toString();
+	}
+	
+	@Override
+	protected void checksourceAndTargetEntityCompliancy() throws NotFoundException, AvailableInAnotherContextException, SchemaViolationException, ResourceRegistryException {
+		String sourceType = sourceEntityManagement.getTypeName();
+		String targetType = targetEntityManagement.getTypeName();
+		
+		RelationType<ResourceType, TET> relationType = getCachedType().getType();
+		
+		ResourceType resourceType = relationType.getSource();
+		TET tet = relationType.getTarget();
+		
+		String requiredSourceType = resourceType.getName();
+		String requiredTargetType = tet.getName();
+		
+		TypesCache typesCache = TypesCache.getInstance();
+		
+		if(!typeSatified(typesCache, requiredSourceType, sourceType)) {
+			String message = getEntityTypeNotValidErrroMessage(RelationElement.SOURCE_PROPERTY, requiredSourceType, sourceType);
+			throw new SchemaViolationException(message);
+		}
+		
+		if(!typeSatified(typesCache, requiredTargetType, targetType)) {
+			String message = getEntityTypeNotValidErrroMessage(RelationElement.TARGET_PROPERTY, requiredTargetType, targetType);
+			throw new SchemaViolationException(message);
+		}
+	}
+	
 	@Override
 	protected OEdge reallyUpdate() throws ResourceRegistryException {
 		
diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/types/relations/RelationTypeDefinitionManagement.java b/src/main/java/org/gcube/informationsystem/resourceregistry/types/relations/RelationTypeDefinitionManagement.java
index 76df687..27e3517 100644
--- a/src/main/java/org/gcube/informationsystem/resourceregistry/types/relations/RelationTypeDefinitionManagement.java
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/types/relations/RelationTypeDefinitionManagement.java
@@ -5,11 +5,13 @@ import java.util.HashMap;
 import org.gcube.informationsystem.base.reference.AccessType;
 import org.gcube.informationsystem.model.reference.relations.Relation;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.AlreadyPresentException;
+import org.gcube.informationsystem.resourceregistry.api.exceptions.AvailableInAnotherContextException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.NotFoundException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.ResourceRegistryException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.relation.RelationNotFoundException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.schema.SchemaAlreadyPresentException;
 import org.gcube.informationsystem.resourceregistry.api.exceptions.schema.SchemaNotFoundException;
+import org.gcube.informationsystem.resourceregistry.api.exceptions.schema.SchemaViolationException;
 import org.gcube.informationsystem.resourceregistry.contexts.ContextUtility;
 import org.gcube.informationsystem.resourceregistry.contexts.security.SecurityContext;
 import org.gcube.informationsystem.resourceregistry.dbinitialization.DatabaseEnvironment;
@@ -208,5 +210,11 @@ public abstract class RelationTypeDefinitionManagement<T extends EntityTypeDefin
 		rtdm.setODatabaseDocument(oDatabaseDocument);
 		return rtdm;
 	}
+	
+	@Override
+	protected void checksourceAndTargetEntityCompliancy() throws NotFoundException, AvailableInAnotherContextException,
+			SchemaViolationException, ResourceRegistryException {
+		// The compliancy is ensured by the code
+	}
 
 }
diff --git a/src/test/java/org/gcube/informationsystem/resourceregistry/instances/InvalidInstancesTest.java b/src/test/java/org/gcube/informationsystem/resourceregistry/instances/InvalidInstancesTest.java
new file mode 100644
index 0000000..f8aae8c
--- /dev/null
+++ b/src/test/java/org/gcube/informationsystem/resourceregistry/instances/InvalidInstancesTest.java
@@ -0,0 +1,54 @@
+package org.gcube.informationsystem.resourceregistry.instances;
+
+import org.gcube.informationsystem.resourceregistry.ContextTest;
+import org.gcube.informationsystem.resourceregistry.api.exceptions.schema.SchemaViolationException;
+import org.gcube.informationsystem.resourceregistry.instances.model.entities.ResourceManagement;
+import org.gcube.informationsystem.resourceregistry.instances.model.relations.IsRelatedToManagement;
+import org.gcube.resourcemanagement.model.reference.entities.resources.Configuration;
+import org.gcube.resourcemanagement.model.reference.entities.resources.EService;
+import org.gcube.resourcemanagement.model.reference.relations.isrelatedto.Activates;
+import org.junit.Test;
+
+public class InvalidInstancesTest extends ContextTest {
+	
+	public static final String ESERVICE = SmartgearResourcesTest.ESERVICE;
+	public static final String ACTIVATES = "{\"header\": {\"@class\": \"Header\",\"creator\": \"luca.frosini\",\"creationTime\": \"2021-02-23 16:45:58.358 +0100\",\"modifiedBy\": \"luca.frosini\",\"uuid\": \"83e9ece1-326c-4d24-a515-0fc6e68f31ef\",\"lastUpdateTime\": \"2021-02-23 16:45:58.358 +0100\"},\"propagationConstraint\": {\"@class\": \"PropagationConstraint\",\"add\": \"propagate\",\"remove\": \"cascade\"},\"@class\": \"Activates\",\"@superClasses\": [\"IsRelatedTo\"],\"source\": {\"header\": {\"@class\": \"Header\",\"creator\": \"luca.frosini\",\"creationTime\": \"2021-02-23 16:45:58.297 +0100\",\"modifiedBy\": \"luca.frosini\",\"uuid\": \"bf665e49-7c54-4984-bafe-a021757a7423\",\"lastUpdateTime\": \"2021-02-23 16:45:58.297 +0100\"},\"@class\": \"Configuration\"},\"target\": {\"header\": {\"@class\": \"Header\",\"creator\": \"luca.frosini\",\"creationTime\": \"2021-02-23 16:45:58.128 +0100\",\"modifiedBy\": \"luca.frosini\",\"uuid\": \"3ace4bd0-e5cd-49a3-97a8-a0a9468ce6d4\",\"lastUpdateTime\": \"2021-02-23 16:45:58.128 +0100\"},\"@class\": \"EService\"}}";
+	public static final String CONFIGURATION = "{\"header\":{\"@class\":\"Header\",\"creator\":\"luca.frosini\",\"creationTime\":\"2021-02-23 16:45:58.382 +0100\",\"modifiedBy\":\"luca.frosini\",\"uuid\":\"bf665e49-7c54-4984-bafe-a021757a7423\",\"lastUpdateTime\":\"2021-02-23 16:45:58.382 +0100\"},\"@class\":\"Configuration\",\"@superClasses\":[\"ConfigurationTemplate\",\"GCubeResource\",\"Resource\"],\"consistsOf\":[{\"header\":{\"@class\":\"Header\",\"creator\":\"luca.frosini\",\"creationTime\":\"2021-02-23 16:45:58.378 +0100\",\"modifiedBy\":\"luca.frosini\",\"uuid\":\"2233f303-497f-433d-9338-6ca16de34c1a\",\"lastUpdateTime\":\"2021-02-23 16:45:58.378 +0100\"},\"propagationConstraint\":{\"@class\":\"PropagationConstraint\",\"add\":\"propagate\",\"remove\":\"cascadeWhenOrphan\"},\"@class\":\"IsIdentifiedBy\",\"@superClasses\":[\"ConsistsOf\"],\"source\":{\"header\":{\"@class\":\"Header\",\"creator\":\"luca.frosini\",\"creationTime\":\"2021-02-23 16:45:58.382 +0100\",\"modifiedBy\":\"luca.frosini\",\"uuid\":\"bf665e49-7c54-4984-bafe-a021757a7423\",\"lastUpdateTime\":\"2021-02-23 16:45:58.382 +0100\"},\"@class\":\"Configuration\",\"@superClasses\":[\"ConfigurationTemplate\",\"GCubeResource\",\"Resource\"]},\"target\":{\"header\":{\"@class\":\"Header\",\"creator\":\"luca.frosini\",\"creationTime\":\"2021-02-23 16:45:58.375 +0100\",\"modifiedBy\":\"luca.frosini\",\"uuid\":\"5efc4c1f-f784-4682-a694-896bd7a3f321\",\"lastUpdateTime\":\"2021-02-23 16:45:58.375 +0100\"},\"type\":\"STRING\",\"persistent\":\"false\",\"value\":\"TEST\",\"@class\":\"IdentifierFacet\",\"@superClasses\":[\"ConsistsOf\"]}},{\"header\":{\"@class\":\"Header\",\"creator\":\"luca.frosini\",\"creationTime\":\"2021-02-23 16:45:58.381 +0100\",\"modifiedBy\":\"luca.frosini\",\"uuid\":\"15055c47-32a1-412c-b6d8-c0d4c831cb95\",\"lastUpdateTime\":\"2021-02-23 16:45:58.381 +0100\"},\"propagationConstraint\":{\"@class\":\"PropagationConstraint\",\"add\":\"propagate\",\"remove\":\"cascadeWhenOrphan\"},\"@class\":\"ConsistsOf\",\"@superClasses\":[\"ConsistsOf\"],\"source\":{\"header\":{\"@class\":\"Header\",\"creator\":\"luca.frosini\",\"creationTime\":\"2021-02-23 16:45:58.382 +0100\",\"modifiedBy\":\"luca.frosini\",\"uuid\":\"bf665e49-7c54-4984-bafe-a021757a7423\",\"lastUpdateTime\":\"2021-02-23 16:45:58.382 +0100\"},\"@class\":\"Configuration\",\"@superClasses\":[\"ConfigurationTemplate\",\"GCubeResource\",\"Resource\"]},\"target\":{\"name\":\"test\",\"header\":{\"@class\":\"Header\",\"creator\":\"luca.frosini\",\"creationTime\":\"2021-02-23 16:45:58.380 +0100\",\"modifiedBy\":\"luca.frosini\",\"uuid\":\"9b71f04c-6f5d-4133-87aa-f37445e206b6\",\"lastUpdateTime\":\"2021-02-23 16:45:58.380 +0100\"},\"value\":\"test\",\"@class\":\"SimplePropertyFacet\",\"@superClasses\":[\"ConsistsOf\"]}}]}"; 
+	
+	
+	@Test(expected = SchemaViolationException.class)
+	public void createInvalidIsRealtedTo() throws Exception {
+		
+		ResourceManagement configurationManagement = new ResourceManagement();
+		ResourceManagement eServiceManagement = new ResourceManagement();
+		try {
+			configurationManagement.setElementType(Configuration.NAME);
+			configurationManagement.setJson(CONFIGURATION);
+			configurationManagement.create();
+			
+			eServiceManagement.setElementType(EService.NAME);
+			eServiceManagement.setJson(ESERVICE);
+			eServiceManagement.create();
+			
+			/*
+			 * Trying to create a relation activates between a Configuration and EService
+			 * The creation MUST fails raising SchemaViolationException because the
+			 * Activates relation is between two Service
+			 *
+			 * The only way to try to create it is using static string because Java classes
+			 * already deny to create and instance of Activates
+			 * 
+			 * Here we want to test how the service behave if a client does not behave properly
+			 */
+			IsRelatedToManagement isRelatedToManagement = new IsRelatedToManagement();
+			isRelatedToManagement.setElementType(Activates.NAME);
+			isRelatedToManagement.setJson(ACTIVATES);
+			isRelatedToManagement.create();
+		}finally {
+			configurationManagement.delete();
+			eServiceManagement.delete();
+		}
+		
+	}
+	
+}