In response to suggestions (initially) from Alan I've started a page that tries to "explain" diagnostics
 
http://www.loc.gov/z3950/agency/zing/srw/diagnostics-notes.html
 
It's just a start, to see if we want to fully develop it. If so I'd like people to contribute examples, descriptions, etc.
 
To avoid duplication of effort, perhaps:
Jan -- sort and scan
Rob -- query
(volunteer) -- records
(volunteer) -- result set
(volunteer) -- stylesheets