Minor detail.

Wouldn't the schema and protocol spec be shorter if version was outside
"operation", i.e.

we'd have
  <zs:version>1.1</zs:version>
  <zs:explainRequest>
      ...
  </zs:explainRequest>
instead of:
  <zs:explainRequest> ... </zs:..>
       <zs:version>1.1</zs:version>
       ...
  </zs:.explainRequest>

where zs="http://www.loc.gov/zing/srw/"

-- Adam