--- a/export_to_metexp_tabular.xml	Fri Apr 04 10:25:19 2014 +0200
+++ b/export_to_metexp_tabular.xml	Thu Apr 24 11:28:38 2014 +0200
@@ -1,6 +1,6 @@
 <tool id="export_to_metexp_tabular" 
     name="METEXP - Tabular file" 
-    version="0.1.0">
+    version="0.2.0">
   <description>Create tabular file for loading into METabolomics EXPlorer database</description>
   <command interpreter="python">
     export_to_metexp_tabular.py $rankfilter_and_caslookup_combi $msclust_quant_file $output_result 
@@ -15,22 +15,33 @@
     	
    <param name="organism" type="text" size="80"
            label="Organism(s) info"
-           help="Metadata information to accompany the results when stored in MetExp DB." /> 	
+           help="Metadata information to accompany the results when stored in MetExp DB." >
+           <validator type="empty_field" message="A value is required."></validator><!-- attribute optional="False" does not seem to work for params so validator is added -->
+    </param>
+            	
    <param name="tissue" type="text" size="80"
            label="Tissue(s) info"
-           help="Metadata information to accompany the results when stored in MetExp DB." />
+           help="Metadata information to accompany the results when stored in MetExp DB."  >
+           <validator type="empty_field" message="A value is required."></validator>
+    </param>
            
    <param name="experiment_name" type="text" size="80"
            label="Experiment name/code"
-           help="Name or code to store the results under. This can help you find the results back in MetExpDB." />  
+           help="Name or code to store the results under. This can help you find the results back in MetExpDB."  >
+           <validator type="empty_field" message="A value is required."></validator>
+    </param>
            
    <param name="user_name" type="text" size="80"
            label="User name"
-           help="User name or code to store the results under. This can help you find the results back in MetExpDB." />  
+           help="User name or code to store the results under. This can help you find the results back in MetExpDB."  >
+           <validator type="empty_field" message="A value is required."></validator>
+    </param>
                    
     <param name="column_type" type="text" size="80"
            label="Column type"
-           help="Column type to report with the results. This can help you find the results back in MetExpDB." />    
+           help="Column type to report with the results. This can help you find the results back in MetExpDB."  >
+           <validator type="empty_field" message="A value is required."></validator>
+    </param>
     
   </inputs>
   <outputs>