Journal of Computer and System Sciences

Managing Editor E.K. Blum Dept. of Mathematics, University of Southern California (USC), 3620 South Vermont Ave., Los Angeles, CA 90089-2532, USA, Editors A.V. Aho New York, NY, USA, J.-Y. Cai Madison, WI, USA, R. Fagin San Jose, CA, USA, J. Hopcroft Ithaca, NY, USA, R.M. Karp Berkeley, CA, USA, D.E. Knuth Stanford, USA, R.E. Miller College Park, MD, USA, C.H. Papadimitriou Berkeley, CA, USA, M. Rabin Cambridge, MA, USA, H. Rogers, Jr. Cambridge, MA, USA, D.S. Scott Berkeley, CA, USA, J.D. Ullman Stanford, USA, L.A. Zadeh Berkeley, CA, USA, Associate Editors M.F. Balcan Atlanta, GA, USA, R. Belohlavek Olomouc, Czech Republic, M. Benedikt Oxford, England, UK, M. Broy Garching bei München, Germany, T. Brun Los Angeles, CA, USA, R. Chang Baltimore, MD, USA, C. Chekuri Urbana, USA, J. Chen College Station, TX, USA, E. Cohen Florham Park, NJ, USA, S. Dasgupta La Jolla, CA, USA, R. de Queiroz Recife, Brazil, M. Fellows Darwin, NT, Australia, H.N. Gabow Boulder, CO, USA, S.A. Goldman St. Louis, MO, USA, M.T. Goodrich Irvine, CA, USA, G. Gottlob Oxford, England, UK, F.C. Graham La Jolla, CA, USA, W. Hodges Okehampton, England, UK, M. Huang Los Angeles, CA, USA, S. Irani Irvine, CA, USA, T. Jiang Riverside, CA, USA, R.E. Kalman Zürich, Switzerland, A.R. Karlin Seattle, WA, USA, S. Khanna Philadelphia, PA, USA, S. Kirkpatrick Jerusalem, Israel, S.R. Kosaraju Baltimore, MD, USA, E. Koutsoupias Athens, Ilisia, Greece, R. Kruse Magdeburg, Germany, R.E. Ladner Seattle, WA, USA, M. Li Waterloo, ON, Canada, W. Maass Graz, Austria, A. Odlyzko Minneapolis, MN, USA, I. Parberry Denton, TX, USA, R. Paturi La Jolla, CA, USA, P. Pevzner La Jolla, CA, USA, G. Plaxton Austin, TX, USA, W. Raskind Tempe, AZ, USA, J. Savage Providence, RI, USA, C. Scheideler Garching bei München, Germany, M. Segal Beer Sheva, Israel, J. Seiferas Rochester, NY, USA, A. Selman Buffalo, NY, USA, R. Shamir Tel Aviv, Israel, E. Sontag Piscataway, NJ, USA, A. Srinivasan College Park, MD, USA, S-H. Teng Los Angeles, CA, USA, V. Terrier Caen, France, J.D. Touch Marina del Rey, CA, USA, M. Vardi Houston, TX, USA, U. Vazirani Berkeley, CA, USA, M. Yannakakis New York, NY, USA, C. Yap New York, NY, USA