1. DEPARTMENT OF COMPUTER AND INFORMATION SCIENCE, UNIVERSITY OF OREGON
2. DEPARTMENT OF COMPUTER AND INFORMATION SCIENCE, UNIVERSITY OF OREGON,
3. JOHN VON NEUMANN INSTITUTE FOR COMPUTING (NIC), FORSCHUNGSZENTRUM
JÜLICH, GERMANY, DEPARTMENT OF COMPUTER SCIENCE, RWTH AACHEN
UNIVERSITY, 52056 AACHEN, GERMANY