Why is there this period in the API? and what time length is it? how is it used?
also is Period.ONE_SEC the shortest period accepted in history and indicators methods?

thanks, also there's https://www.dukascopy.com/client/javadoc/com/dukascopy/api/feed/IBarFeedListener.html

Please use the approach which is described in wiki - the one with IFeedListener, as it provides you maximum flexibility.

ok noted.
Feed is much better and flexible than the default onBar method in IStrategy, you could remove it in the future maybe

Just because you don't find it useful, maybe there are other users out there who indeed using this method, don't you think so?

Removal of any method from an interface would cause all current implementations fail to compile. Hence, all existing strategies would need to get rewritten and recompiled. So, obviously, we are not going to do this.