xviii Acknowledgments and insightful feedback.They include:S.Banerjee,M.Ben-Ari,H.Berliner,S.D Brookes,A.K.Chandra,N.Dershowitz,R.Fagin,A.Fiat,J.Gal-Ezer,A.Heydon, C.A.R.Hoare,L.Kari,D.E.Knuth,Q.Limmois,W.Pollock,R.Raz,Z.Reisel, E.Roberts,R.Rosner,S.Safra,J.Seiferas,D.Sherman,R.Sherman,B.Simons, D.Sleator,R.Topor,D.Tygar,M.Vardi,P.Wegner,and L.Zuck. D.H.P1: GIG PE002-FM PE002-Harel PE002-Harel-FM-v1.cls March 19, 2004 19:35 xviii Acknowledgments and insightful feedback. They include: S. Banerjee, M. Ben-Ari, H. Berliner, S. D. Brookes, A. K. Chandra, N. Dershowitz, R. Fagin, A. Fiat, J. Gal-Ezer, A. Heydon, C. A. R. Hoare, L. Kari, D. E. Knuth, Q. Limmois, W. Pollock, R. Raz, Z. Reisel, E. Roberts, R. Rosner, S. Safra, J. Seiferas, D. Sherman, R. Sherman, B. Simons, D. Sleator, R. Topor, D. Tygar, M. Vardi, P. Wegner, and L. Zuck. D.H