restricted stringXMLListType so it can't start or end with spaces

SI_Format.xsd

@@ -1444,11 +1444,18 @@
     <xs:simpleType name="stringXMLListType">
         <xs:annotation>
             <xs:documentation xml:lang="en">
-                Type providing listing of strings (xs:string) 
-                with separation by blank spaces.
+                Type providing listing of strings (xs:string)
+                with separation by blank spaces, ensuring no
+                string starts or ends with spaces.
             </xs:documentation>
         </xs:annotation>
-        <xs:list itemType="xs:string" />
+        <xs:list>
+            <xs:simpleType>
+                <xs:restriction base="xs:string">
+                    <xs:pattern value="[^ ](.*[^ ])?"/>
+                </xs:restriction>
+            </xs:simpleType>
+        </xs:list>
     </xs:simpleType>