Is there a recommendation on how I should interpret a query?

When looking at queries, people all seem to have there own way of searching.

Say a query comes in like:
bush clinton taft washington
Probably, the person who entered this is looking for something on American presidents. He'd expect to get back something like
the life story of bill clinton.pdf
the life story of george bush.pdf
To put it in other words, he's wants to search usign a OR operator.

However, someone else will look for
how to plant a bush.mpg
and doesn't expect to get anything else back than that. He needs an AND operator, and doesn't care for the life story of george bush (can you blame him?)

Any suggestions? Is there a *standard* in this?


Also, some queries end on
urn:sha1:HQ39875SDJHSF09FSDFSDF
or something like that.
Others appear to contain xml

What should I do with them, since I assume these are applications-specific thingies. Must I try to interpret them?


Thanx