From the docs for
List of tags delimited by semi-colons of which at least one must be on a question
Yet, when I execute this query (
http://api.stackoverflow.com/1.0/search?tagged=java;algorithm&sort=creation&min=1296897084&pagesize=2), it returns a single 8-hours old question, tagged both algorithm and java. Naturally, since that time lot's of newer questions has been posted in both
java tags separately.
It looks like, current interpretation of this parameter is each one must be on a question instead.