diff --git a/src/main/java/org/gcube/data/analysis/dminvocation/model/DataMinerInputParams.java b/src/main/java/org/gcube/data/analysis/dminvocation/model/DataMinerInputParams.java
index 73e5f76..7e898ab 100644
--- a/src/main/java/org/gcube/data/analysis/dminvocation/model/DataMinerInputParams.java
+++ b/src/main/java/org/gcube/data/analysis/dminvocation/model/DataMinerInputParams.java
@@ -38,7 +38,7 @@ public class DataMinerInputParams implements Serializable{
 	 */
 	private static final long serialVersionUID = -7241629940190729604L;
 
-	@XmlElement(name = "param")
+	@XmlElement(name = "param", required=true, nillable=false)
 	private List<DataMinerParam> listParam;
 
 
diff --git a/src/main/java/org/gcube/data/analysis/dminvocation/model/DataMinerInvocation.java b/src/main/java/org/gcube/data/analysis/dminvocation/model/DataMinerInvocation.java
index f0ba1dd..50dd7d1 100644
--- a/src/main/java/org/gcube/data/analysis/dminvocation/model/DataMinerInvocation.java
+++ b/src/main/java/org/gcube/data/analysis/dminvocation/model/DataMinerInvocation.java
@@ -35,13 +35,13 @@ public class DataMinerInvocation implements Serializable{
 
 	private static final long serialVersionUID = -3642902539322040226L;
 
-	@XmlElement(name = "operator-id")
+	@XmlElement(name = "operator-id", required=true, nillable=false)
 	private String operatorId;
 
 	@XmlElement(name = "action", required=true, nillable=false)
-	private ActionType actionType;
+	private ActionType actionType = ActionType.RUN;
 
-	@XmlElement(name = "parameters", required=true, nillable=false)
+	@XmlElement(name = "parameters", required=false, nillable=true)
 	private DataMinerParameters parameters;
 
 }
diff --git a/src/main/java/org/gcube/data/analysis/dminvocation/model/DataMinerParameters.java b/src/main/java/org/gcube/data/analysis/dminvocation/model/DataMinerParameters.java
index 283af88..6175839 100644
--- a/src/main/java/org/gcube/data/analysis/dminvocation/model/DataMinerParameters.java
+++ b/src/main/java/org/gcube/data/analysis/dminvocation/model/DataMinerParameters.java
@@ -37,9 +37,9 @@ public class DataMinerParameters implements Serializable{
 	 *
 	 */
 	private static final long serialVersionUID = 8298755690515099551L;
-	@XmlElement(name = "input", required=true)
+	@XmlElement(name = "input", required=true, nillable=false)
 	private DataMinerInputParams input;
-	@XmlElement(name = "output", required=false)
+	@XmlElement(name = "output", required=false, nillable=true)
 	private DataMinerOutputParams output;
 
 }