ocr: Additional copies may be Phone orders: ordered prepaid from: +1 800 342 6626 (USA and Canada) ACM Order Department +12 212 626 0500 P.O. Box 11405 (All other countries) Church Street Station Fax orders: New' York, NY 10286-1405 +1 212 944 1318. Email: acmhelp@acm.org Copyright 2001 Association for Computing ACM Order # 428013 Machinery (ACM) ACM ISBN # 1-58113-401-0