Copyright
© 2006 by the Association for Computing Machinery, Inc. (ACM).
Permission to make digital or hard copies of portions 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 the
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 a fee. Request permission to
republish from: Publications Dept., ACM, Inc. Fax +1 (212)
869-0481 or permissions@acm.org
For other copying of articles that carry a code at the bottom of
the first or last page, 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.
Notice to Past Authors of ACM-Published Articles
ACM intends to
create a complete electronic archive of all articles and/or
other material previously published by ACM. If you have written
a work that has been previously published by ACM in any journal
or conference proceedings prior to 1978, or any SIG Newsletter
at any time, and you do NOT want this work to appear in the ACM
Digital Library, please inform permissions@acm.org, stating the
title of the work, the author(s), and where and when published.
ISBN:
1-59593-587-8
Additional copies
may be ordered prepaid from:
ACM Order Department
PO Box 11405, New York, NY 10286-1405