Rapid and Coordinated Responses: Patterns for Real-Time QoS Adaptation
Citation:
Paul Rubel, Joseph Loyall, Michael
Atighetchi, Partha Pal, and Richard Schantz. Rapid and Coordinated
Responses: Patterns for Real-Time QoS Adaptation. The 10th Conference
on Pattern Languages of Programs 2003, Patterns and Pattern Languages
for Distributed Real-Time and Embedded Systems, Monticello, Illinois,
September 8-12, 2003.
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Abstract
Many Distributed Real-time Embedded (DRE)
applications need to adapt to changing conditions. They are often
subject to dynamic conditions, such as resource contention and
availability. These conditions are more dynamic in DRE systems than
in traditional static real-time systems because DRE systems are spread
among networked, often heterogeneous platforms, which can consist of a
variable number of communicating nodes, which use resources (such as
wireless, tactical, and satellite networks) that are subject to
noise, failure, or attack. Adaptation in these systems has to satisfy
two seemingly conflicting forces. The first is that adaptation has to
fit within the real-time constraints of the DRE system and must rely
on whatever information is available at that time. Taking too much
time to adapt can lead to missed deadlines and/or failure to meet
mission critical requirements. The second force is that adaptations
must be consistent with the requirements of the entire distributed
system, i.e., local adaptations must work in conjunction with other
local adaptations and be consistent with the requirements of the
entire DRE system or system of systems. This paper presents two
constituent patterns and a compound pattern for implementing rapid
local adaptations, reacting and controlling limited local conditions,
and coordinating multiple local adaptations for subsystem or
system-wide requirements. These patterns are necessary for DRE
systems that can maintain their critical QoS and mission requirements
in dynamic environments.
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