diff --git a/lib/workflowmgr/schema_with_metatasks.rng b/lib/workflowmgr/schema_with_metatasks.rng
index cd75076..d653ee6 100644
--- a/lib/workflowmgr/schema_with_metatasks.rng
+++ b/lib/workflowmgr/schema_with_metatasks.rng
@@ -465,14 +465,30 @@
           </element>
         </optional>
 
-        <!-- Either one cores tag or one nodes tag-->
+        <!-- Either one cores tag or one nodes or at least one native tag is required-->
         <choice>
-          <element name="cores">
-            <data type="positiveInteger"/>          
-          </element>
-          <element name="nodes">
-            <data type="string"/>          
-          </element>
+          <interleave>
+	    <choice>
+	      <element name="cores">
+		<data type="positiveInteger"/>
+	      </element>
+	      <element name="nodes">
+		<data type="string"/>
+	      </element>
+	    </choice>
+	    <optional>
+              <oneOrMore>
+	        <element name="native">
+		  <ref name="compoundTimeString"/>
+	        </element>
+              </oneOrMore>
+	    </optional>
+          </interleave>
+          <oneOrMore>
+            <element name="native">
+              <ref name="compoundTimeString"/>
+            </element>
+          </oneOrMore>
         </choice>
 
         <!-- One walltime tag -->
@@ -518,15 +534,6 @@
           </element>
         </optional>
 
-        <!-- One or more native tags -->
-        <optional>
-          <oneOrMore>
-            <element name="native">
-              <ref name="compoundTimeString"/>
-            </element>
-          </oneOrMore>
-        </optional>
-
         <!-- Optional nodesize tag -->
         <optional>
           <element name="nodesize">
diff --git a/lib/workflowmgr/schema_without_metatasks.rng b/lib/workflowmgr/schema_without_metatasks.rng
index 2b9d97c..79cab40 100644
--- a/lib/workflowmgr/schema_without_metatasks.rng
+++ b/lib/workflowmgr/schema_without_metatasks.rng
@@ -446,14 +446,30 @@
           </element>
         </optional>
 
-        <!-- Either one cores tag or one nodes tag-->
+        <!-- Either one cores tag or one nodes or at least one native tag is required-->
         <choice>
-          <element name="cores">
-            <data type="positiveInteger"/>
-          </element>
-          <element name="nodes">
-            <data type="string"/>
-          </element>
+          <interleave>
+	    <choice>
+	      <element name="cores">
+		<data type="positiveInteger"/>
+	      </element>
+	      <element name="nodes">
+		<data type="string"/>
+	      </element>
+	    </choice>
+	    <optional>
+              <oneOrMore>
+	        <element name="native">
+		  <ref name="compoundTimeString"/>
+	        </element>
+              </oneOrMore>
+	    </optional>
+          </interleave>
+          <oneOrMore>
+            <element name="native">
+              <ref name="compoundTimeString"/>
+            </element>
+          </oneOrMore>
         </choice>
 
         <!-- One walltime tag -->
@@ -499,15 +515,6 @@
           </element>
         </optional>
 
-        <!-- Zero or more native tags -->
-        <optional>
-          <oneOrMore>
-            <element name="native">
-              <ref name="compoundTimeString"/>
-            </element>
-          </oneOrMore>
-        </optional>
-
         <!-- Optional nodesize tag -->
         <optional>
           <element name="nodesize">