We have found it useful, in our IRSpy register of Z39.50 and SRU
targets, to add a measure of "reliability" for each server, expressed
as a percentage and measuring what proportion of all the connections
we've tried to make have been successful. Using this, we can search
for only those targets that are up, say, 90% of the time. (This
searching facility is not yet wired out to the public Web UI at
http://irspy.indexdata.com/ but it will be.)
In order to enable searching in this way via SRU, we need to add a
"reliability" index -- so far as we can determine, there is no such
index in any of the existing context sets. This seems like a good
match for ZeeRex, which is all about describing databases and the
services that provide them, so we propose that the new index be added
to the ZeeRex context set. We propose a brief, non-prescriptive
semantics statement like "an integer in the range 0-100 indicating how
reliable the server had been found to be".
As an aside, the LC page about context sets,
links the ZeeRex set to the location:
but this URL has gone away since Rob Sanderson left the Cheshire
project. So have the Record Metadata set ("rec"), the Network
Resource Information set ("net"), the Collectable Card Games set
("ccg") though that one will probably not cause so many problems, and
the Relevance Ranking set ("rel"). This is very bad.
Some, but not all, of those sets are available as old versions on the
WayBack Machine: for example, there is an old "rec" set at
but I have not been able to get it to give me an old "zeerex" set.
For that reason, I have resurrected an old copy of the ZeeRex site as
it was before I foolishly handed it over to Rob, and it is now
In particular, the ZeeRex context set for CQL is at:
I hope this is useful to more than just me.