Complex sentence: The conference was a 3-day event and was held from 2003-2010 in Ottawa, Canada with the exception of the 2009 summit, which was held in Montreal, Canada.
Split into simpler sentences: The conference was a 3-day event and has been held each year since 2003. It has always been held in Ottawa, Canada with the exception of the 2009 summit, which was held in Montreal, Canada.