TITLE: Replicated Condition Monitoring

AUTHORS:
Yongqiang Huang and Hector Garcia-Molina
Department of Computer Science
Stanford University
Stanford, CA 94305
{yhuang, hector}@cs.stanford.edu

ABSTRACT:
A condition monitoring system tracks real-world variables and alerts
users when a predefined condition becomes true, e.g., when stock price
drops, or when a nuclear reactor overheats.  Replication of monitoring
servers can reduce the probability that an important alert is missed.
However, replicated independent servers can sometimes report
"conflicting" alerts to the user, causing confusion.  In this paper,
we study the problem of replicated condition monitoring.  We identify
and formally define three desirable properties of a replicated system,
namely, orderedness, consistency, and completeness.  We propose new
monitoring algorithms that enforce some or all of the desired
properties in different scenarios.