Alvin AuYoung Laura Rit Sohn Wiener John Wilkes Service contracts and aggregate utility functions. 119-131 2006 HPDC http://doi.ieeecomputersociety.org/10.1109/HPDC.2006.1652143 conf/hpdc/2006 db/conf/hpdc/hpdc2006.html#AuYoungRWW06