Currently it is not easy with SRU/W to broadcast the same query to many
SRU/W servers because one has to take into account all the differences
between different servers. Especially in metasearching I think it would
be convenient when there was a possibility to send a query saying "give
me what is closest to this query" and allow different servers to respond
with a servers choice according to one or more predefined responses. The
responses could a.o. be:
1) searchRetrieveResponse
2) scanResponse
3) results of a fuzzy match
4) number of hits for different access points
5) etc.

Without having to find out how to translate a query for different
targets such an "give me the best you can" request returns one or more
response blocks and the client can use the ones that it understands to
generate guidance to the user to improve his search. It is not the same
as the "x-scanOnSearchFail" parameter, because it can also apply to
other situations. For example when there are thousands of hits a server
could provide a response block in which it gives the number of hits for
different indexes. The client can use this to propose new searches, even
with indexes that it would not have offered otherwise.

I remember having proposed something like this earlier and we will
implement this as a private extension. However,  in the context of the
NISO metaseach meeting there may be more support for this concept.

1) Who would support a proposal for extending SRU/SRW with such an
operation?
2) Should this be done via a new x-parameter or via a new operation?

BTW Who of this group is attending the NISO metasearch meeting?

Theo