I think the specification is clear about that.
So there is an overhead but that may not be the main issue.
The issue might be more about defining a correct schema. If a field can be
null then all clients should handle the case when the field is indeed null.
That's a 'hygiene issue' (or data quality issue if your prefer), like with
a database schema.
On Fri, Mar 14, 2014 at 9:15 AM, Fengyun RAO <[EMAIL PROTECTED]> wrote: