School of Computing Science, Simon Fraser University, Burnaby, Canada, V5A 1S6. fhach@cs.sfu.ca|School of Computing Science, Simon Fraser University, Burnaby, Canada, V5A 1S6. fhach@cs.sfu.ca|School of Computing Science, Simon Fraser University, Burnaby, Canada, V5A 1S6. fhach@cs.sfu.ca|School of Computing Science, Simon Fraser University, Burnaby, Canada, V5A 1S6. fhach@cs.sfu.ca