A Technical History of the SEI

analysis as well as model tuning for runtime deployment of Q-RAM models. Guidance was developed
for model tuning of the Q-RAM. Model tuning involves specifying a consistent set of Q-
RAM model parameters, including the utility values for quality dimensions and task weights. A
notation was also developed to support the expression of cross-task quality-level constraints to
achieve predictable degradation behavior [Rajkumar 1997]. The Visual Q-RAM software tool was
enhanced to support use-scenario walkthroughs and development
of models from predefined libraries of task
types. Use of this technology in DoD contexts was
demonstrated by developing a set of examples; these included
helicopter pilot mission support, phased array radar
bandwidth allocation, and radar target-tracking algorithm
selection.
Real-time queueing theory provides accurate timing behavior
predictions of real-time systems having stochastic
workloads. The theory can be used to assess the ability
of a system to meet the timing requirements under heavy
traffic conditions. It complements scheduling theories
such as generalized rate monotonic scheduling. Visual
RTQT is a tool that demonstrates the practicality of using
RTQT. Important progress was made in the development
of RTQT and its application to avionics and communication
systems [Lehoczky 1996]. RTQT is a
significant innovation in the design and scheduling of
real-time systems in that it is capable of making exact
predictions of a system’s ability to meet the timing requirements
of real-time tasks where task arrivals and
computation requirements are stochastic. It extends
methodologies such as GRMA to a greatly broadened
framework. The RTQT project innovations include development
of an RTQT-based analysis of the temporal
behavior of the F-22 avionics challenge problem and an
RTQT analysis for feed-forward queuing networks and
for acyclic networks, leading to an analysis tool for the
determination of end-to-end schedulability requirements.
The View from Others
This group [CMU IMPACT]
demonstrated all proposed objectives
from the DASADA literature.
This group works closely with
Lockheed Martin on real time
scheduling and context testing on
the F-16 avionics platforms. CMU
is doing breadboard testing and
creating prototypes for a new advanced
avionics suite proposed for
future aircraft development. An
evaluation of this system indicated
this group is ready to move on to
the next phase of the DASADA
program. (pp. 63-64)
Out of the 19 projects, there is
only a handful that should be considered
for future funding based
upon their level of effort over the
past several months, as well as
their level of technology maturity
to be able in the next year to actually
provide a component to insert
into the DASADA Dynamic Assembly
Toolkit. [One of those projects
is] CMU’s Integrated Methods for
Predictive Analytic Composition
and Tradeoff (IMPACT). (pp. 76-
77)
– Wayne S. Mandak and
Charles A. Stowell,
[Mandak 2001]
Hierarchical scheduling is a method based on GRMA
that enables a single schedulable physical resource, such
as a processor, to be partitioned into multiple isolated
virtual resources. Different algorithms and analysis techniques
can be used in each of the virtual resources, and
changes in the temporal properties within one virtual resource
do not impact the temporal behavior within other virtual resources [Saewong 2002].
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