... There should also be a standard mechanism for multiple searches and
complex searches....
"ANSI/NISO Z39.58-1992 Common Command Language for On-Line Interactive
Information Retrieval."
ANSI documents are generally not available for free; major university
libraries often have trouble maintaining a collection of ANSI documents
because of their high cost and the fact that there are so many of very
limited utility. Z39.58 is availible from ANSI for USD $48.00 --
http://webstore.ansi.org/ansidocstore/product.asp?sku=ANSI%2FNISO+Z39%2E58%2D1992
-- but the fact that a quick reference guide for it can't be found via
AltaVista or Google should give you an idea of how unpopular it is.
Z39.58 is more complicated but has fewer features than the command
syntax of either of those those major search engines.
In my opinion, the only standard needed for search engines in an
on-line command reference guide for the seach syntax, e.g. "search
tips" or "help searching". There are still a lot of experimental
features being sorted out, so standardization at that level might
likely just get in the way at present. Someday it is bound to occur.
Cheers,
James