Commit in docs/usefor (usepro.xml)

    Date: Sunday, March 1, 2009 @ 18:28:39
  Author: eagle
Revision: 5766

Clarify handling of <chksernr> and change the example to use YYYYMMDDNN.
Suggest string comparisons for potentially long serial numbers.

Modified:
  docs/usefor/usepro.xml

Modified: docs/usefor/usepro.xml
===================================================================
--- docs/usefor/usepro.xml	2009-03-01 22:43:59 UTC (rev 5765)
+++ docs/usefor/usepro.xml	2009-03-02 02:28:39 UTC (rev 5766)
@@ -1962,19 +1962,28 @@
           or sub-hierarchy with a smaller &lt;chksernr> value or with no
           &lt;chksernr> value.</t>
 
+          <t>There is no upper limit on the length of &lt;chksernr>
+          other than the limitation on the length of header fields.
+          Implementations may therefore want to do comparisons by
+          zero-padding the shorter of two &lt;chksernr> values on the
+          left and then doing a string comparison rather than assuming
+          &lt;chksernr> can be manipulated as a number.</t>
+
           <figure>
             <preamble>For example, the following Control header
             field</preamble>
 
             <artwork>
-      Control: checkgroups de !de.alt #248
+      Control: checkgroups de !de.alt #2009021301
             </artwork>
 
             <postamble>indicates the body of the message will list every
             newsgroup in the de.* hierarchy, excepting the de.alt.*
             sub-hierarchy, and should not be honored if a checkgroups
-            control message with a serial number greater than 248 was
-            previously honored.</postamble>
+            control message with a serial number greater than 2009021301
+            was previously honored.  The serial number in this example
+            was formed from the date in YYYYMMDD format followed by a
+            two-digit sequence number within that date.</postamble>
           </figure>
 
           <t>The body of the message is an entity of type