Co-Chairs Ronald F. Boisvert and
Gul Agha; Michel Beaudouin-Lafon;
Jack Davidson; Nikil Dutt; Carol Hutchins;
Ee-Peng Lim; M. Tamer Ozsu; Vincent Shen;
Mary Lou Soffa; Ricardo Baeza-Yates
Subscriptions: Annual cost to ACM
members: $54.00, student members: $49.00,
individual nonmembers: $105.00,
nonmember institutions: $105.00.
Single copies are $13.00 to members, $20.00
to nonmembers. Please send orders prepaid
plus $7.00 for domestic shipping and handling
($8.00 for foreign) to ACM Order Dept.,
P.O. Box 11414, New York, NY 10257 or call
+1-212-626-0500. For credit card orders, call
Order personnel available 8:30–4: 30 EST.
After hours, please leave message and order
personnel will return your call.
Change of address: firstname.lastname@example.org
For other services, questions, or information:
Copyright © 2009 by Association for
Computing Machinery, Inc. (ACM).
Permission to make digital or hard copies of
part or all of this work for personal or classroom use is granted without fee provided
that copies are not made or distributed for
profit or commercial advantage and that
copies bear this notice and full citation on
the first page. Copyright for components of
this work owned by others than ACM must
be honored. Abstracting with credit is
permitted. To copy otherwise, to republish,
to post on servers, or to redistribute to lists,
requires prior specific permission and/or
fee. Request permission to publish from:
Publications Dept., ACM, Inc. Fax +1-212-
869-0481 or email email@example.com
For other copying of articles that carry a
code at the bottom of the first or last page or
screen display, copying is permitted provided
that the per-copy fee indicated in the code is
paid through the Copyright Clearance Center,
222 Rosewood Drive, Danvers, MA 01923,
+1-978-750-8400, +1-978-750-4470 (fax).
ACM, 2 Penn Plaza, Suite 701,
New York, New York 10121-0701,
+1-212-869-7440, FAX: +1-212-869-0481
Executive Editor: Andrew Rosenbloom
Managing Editor: Denise Doig
Art Director: Andrij Borys
Production Manager: Lynn D’Addesio-Kraus
Media Sales: Jennifer Ruzicka
Books: Michele Tepper
Business the 8th Layer: Lynn Greiner
Net News: Alan Zeichick
Putting IT Together: Win Treese
Editorial advisory board:
David S. Isenberg
Donald A. Norman
ACM Advertising Department
2 Penn Plaza, Suite 701
New York, NY 10121-0701
Fax (212) 869-0481
Director of Media Sales:
net Worker (ISSN 1091-3556) is published
four times a year in March, June, September,
and December by the Association for
Computing Machinery, Inc., 2 Penn Plaza,
Suite 701, New York, NY 10121-0701.
Periodical class postage paid at New York,
NY 10001, and at additional mailing offices.
Printed in the U.S.A.
Send address changes to:
net Worker, ACM, 2 Penn Plaza, Suite 701,
New York, NY 10121-0701.