diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/OperationValidator.java b/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/OperationValidator.java
new file mode 100644
index 0000000..54bf0c1
--- /dev/null
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/OperationValidator.java
@@ -0,0 +1,16 @@
+package org.gcube.informationsystem.resourceregistry.instances.model;
+
+import java.util.Map;
+import java.util.UUID;
+
+import org.gcube.com.fasterxml.jackson.databind.JsonNode;
+import org.gcube.informationsystem.resourceregistry.api.exceptions.ResourceRegistryException;
+
+/**
+ * @author Luca Frosini (ISTI - CNR)
+ */
+public interface OperationValidator {
+	
+	public boolean isValidOperation(Map<UUID, JsonNode> affectedInstances) throws ResourceRegistryException;
+	
+}
diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/SharingOperationValidator.java b/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/SharingOperationValidator.java
new file mode 100644
index 0000000..3beea67
--- /dev/null
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/SharingOperationValidator.java
@@ -0,0 +1,81 @@
+package org.gcube.informationsystem.resourceregistry.instances.model;
+
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+
+import org.gcube.com.fasterxml.jackson.databind.JsonNode;
+import org.gcube.informationsystem.base.reference.Element;
+import org.gcube.informationsystem.resourceregistry.api.exceptions.ResourceRegistryException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class SharingOperationValidator implements OperationValidator {
+
+	protected static Logger logger = LoggerFactory.getLogger(SharingOperationValidator.class);
+	
+	protected final Map<UUID, JsonNode> expectedInstaces;
+	protected final String operation;
+	
+	public SharingOperationValidator(Map<UUID, JsonNode> expectedInstaces, String operation) {
+		this.expectedInstaces = expectedInstaces;
+		this.operation = operation;
+	}
+	
+	@Override
+	public boolean isValidOperation(Map<UUID, JsonNode> affectedInstances) throws ResourceRegistryException {
+		Set<UUID> expectedUUIDSet = expectedInstaces.keySet();
+		Set<UUID> affectedUUIDSet = new HashSet<>(affectedInstances.keySet());
+		
+		affectedUUIDSet.removeAll(expectedUUIDSet);
+		if(affectedUUIDSet.size()>0) {
+			StringBuffer stringBuffer = new StringBuffer();
+			stringBuffer.append("To keep the integrity of the IS the operation ");
+			stringBuffer.append(operation);
+			stringBuffer.append(" affects more instances than the requested by the client. The operation will be aborted. ");
+			stringBuffer.append("Additional affected instances are ");
+			stringBuffer.append(affectedUUIDSet.toString());
+			String errorMessage = stringBuffer.toString();
+			logger.error(errorMessage);
+			throw new ResourceRegistryException(errorMessage);
+		}
+				
+		for(UUID expectedUUID : expectedUUIDSet) {
+			JsonNode expectedJsonNode = expectedInstaces.get(expectedUUID);
+			JsonNode affectedJsonNode = affectedInstances.get(expectedUUID);
+			if(affectedJsonNode==null) {
+				StringBuffer stringBuffer = new StringBuffer();
+				stringBuffer.append("The operation ");
+				stringBuffer.append(operation);
+				stringBuffer.append(" did not affected the instance with UUID ");
+				stringBuffer.append(expectedUUID.toString());
+				stringBuffer.append(" ");
+				stringBuffer.append(expectedJsonNode);
+				stringBuffer.append(". This should not occur. Please contact the administrator.");
+				String errorMessage = stringBuffer.toString();
+				logger.error(errorMessage);
+				throw new ResourceRegistryException(errorMessage);
+			}
+			
+			String expectedType = expectedJsonNode.get(Element.CLASS_PROPERTY).asText();
+			String affectedType = affectedJsonNode.get(Element.CLASS_PROPERTY).asText();
+			if(expectedType.compareTo(affectedType)!=0) {
+				StringBuffer stringBuffer = new StringBuffer();
+				stringBuffer.append("The expected type of the instance with UUID ");
+				stringBuffer.append(expectedUUID);
+				stringBuffer.append(" is ");
+				stringBuffer.append(expectedType);
+				stringBuffer.append(". Instead the effective instance with such UUID is");
+				stringBuffer.append(affectedType);
+				stringBuffer.append(". The operation has been aborted.");
+				String errorMessage = stringBuffer.toString();
+				logger.error(errorMessage);
+				throw new ResourceRegistryException(errorMessage);
+			}
+		}
+		
+		return true;
+	}
+
+}