diff --git a/src/main/java/org/gcube/common/workspacetaskexecutor/dataminer/WorkspaceDataMinerTaskExecutor.java b/src/main/java/org/gcube/common/workspacetaskexecutor/dataminer/WorkspaceDataMinerTaskExecutor.java
index d56a3cc..1162ced 100644
--- a/src/main/java/org/gcube/common/workspacetaskexecutor/dataminer/WorkspaceDataMinerTaskExecutor.java
+++ b/src/main/java/org/gcube/common/workspacetaskexecutor/dataminer/WorkspaceDataMinerTaskExecutor.java
@@ -443,24 +443,28 @@ public class WorkspaceDataMinerTaskExecutor implements ExecutableTask<TaskConfig
 	/**
 	 * Gets the list operators.
 	 *
-	 * @param filterForParameterNames the filter for parameter names. It returns only {@link TaskOperator} matching the input filters
+	 * @param filterForParameterTypes the filter for parameter types. It returns only {@link TaskOperator} matching the input filters
 	 * @param operator the operator applied to the filters. It must be of type {@link FilterOperator}
 	 * @return the list operators
 	 * @throws Exception the exception
 	 */
-	public List<TaskOperator> getListOperators(String[] filterForParameterNames, FilterOperator operator) throws Exception{
-
-		Validate.notNull(operator, "The "+FilterOperator.class.getSimpleName()+" passed is null");
+	public List<TaskOperator> getListOperators(String[] filterForParameterTypes, FilterOperator operator) throws Exception{
+		logger.info("Getting list operators applying filters: "+filterForParameterTypes+", operator: "+operator);
 
 		DataMinerAccessPoint dap = getDataMinerAccessPoint();
 
-		if(filterForParameterNames==null || filterForParameterNames.length==0){
+		if(filterForParameterTypes==null || filterForParameterTypes.length==0){
 			logger.info("Returning "+dap.getListOperators().size()+ " operator/s. No filter applied");
 			return dap.getListOperators();
 		}
 
 		List<TaskOperator> filteredListOperators = new ArrayList<TaskOperator>(dap.getListOperators().size());
 
+		if(operator==null){
+			operator = FilterOperator.LOGICAL_OR;
+			logger.info("The input parameter "+FilterOperator.class.getSimpleName() +" is null, using default "+operator);
+		}
+
 		//APPLYING FILTERS ON PARAMETER NAME/TYPE
 		for (TaskOperator taskOperator : dap.getListOperators()) {
 			logger.trace("***Algor: "+taskOperator.getName());
@@ -469,8 +473,8 @@ public class WorkspaceDataMinerTaskExecutor implements ExecutableTask<TaskConfig
 
 			for (TaskParameter taskParameter : io) {
 				logger.trace("key: "+taskParameter.getKey() + ", value: "+taskParameter.getValue() +", defaultValue: "+taskParameter.getDefaultValue());
-				for (String filterParameterName : filterForParameterNames) {
-					if(taskParameter.getKey().compareToIgnoreCase(filterParameterName)==0){
+				for (String filterParameterName : filterForParameterTypes) {
+					if(taskParameter.getType().getType().compareToIgnoreCase(filterParameterName)==0){
 						filterPassed++;
 					}
 				}
@@ -478,12 +482,16 @@ public class WorkspaceDataMinerTaskExecutor implements ExecutableTask<TaskConfig
 
 			if(operator.equals(FilterOperator.LOGICAL_OR) && filterPassed>=1){
 				filteredListOperators.add(taskOperator);
+				logger.debug("Added operator: "+taskOperator + " It is matching "+FilterOperator.LOGICAL_OR +" and filterPassed>=1");
 			//IN AND ALL FILTERS MUST BE MATCHED
-			}else if(operator.equals(FilterOperator.LOGICAL_AND) && filterPassed==filterForParameterNames.length){
+			}else if(operator.equals(FilterOperator.LOGICAL_AND) && filterPassed==filterForParameterTypes.length){
 				filteredListOperators.add(taskOperator);
+				logger.debug("Added operator: "+taskOperator + " It is matching "+FilterOperator.LOGICAL_AND +" and filterPassed==filterForParameterNames.length");
+			}
+			else{
+				logger.info("Removed operator: "+taskOperator + " It does not match the filters: "+filterForParameterTypes);
+				filteredListOperators.remove(taskOperator);
 			}
-			else
-				logger.info("Removed operator: "+taskOperator + " It does not match filters: "+filterForParameterNames);
 
 		}