On Thu, 22 Jun 2006, Charley Pennell wrote:
> [...] If you have ever used a local Z39.50 client, LC's Z39.50 gateway
> (http://www.loc.gov/z3950/gateway.html), or one of the Web catalog
> gateways, you know how often catalog IP addresses change and how
> maintaining lists of thousands of these would be a never-ending task.
When we did the ROADS software many moons ago, one of the reasons we used
the WHOIS++ directory search protocol rather than Z39.50 directly was that
WHOIS++ came with the concept of "Forward Knowledge" to allow query
routing to servers that were likely to know about the subject even if your
local server didn't. The idea was that the local server knew about a few
other servers that it would swap "centroids" with (basically cut down data
sets that hinted at what each server knows about).
When the user queried his local server, they could get matches from the
local database and also pointers to other servers that could help. The
client software (CGI scripts!) could then query those servers to get
results. Some of those results might be pointers to yet more servers and
so on and so on. The query routing could be done either manually asking
the user if they wanted to expand their search or automatically following
forward knowledge paths to a given depth.
It never really got used much by the services that used ROADS other than
for some demos and is dead tech now, but query routing and forward
knowledge might be worth considering in future distributed, loosely
coupled library systems.
Jim'll
Received on Mon Jun 26 2006 - 12:35:36 EDT