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<title>Design-to-time Real-time Scheduling</title>
<h1>Design-to-time Real-time Scheduling</h1>

  Design-to-time is an approach to real-time problem solving in situations
where multiple methods exist for many tasks that a system needs to solve.
Design-to-time involves designing a solution to a problem that uses all
available resources to maximize the solution quality within the available
time.  One important area of research has focused on interdependencies that
may exist between methods, such as the execution of one method enabling the
execution of another, or the use of a rough approximation by one method
negatively affecting the performance of a method that uses its result.<p>

The methodology is known as design-to-time because it advocates the use
of all available time to generate the best solutions possible.  It is a
problem-solving method of the type described by D'Ambrosio as
those which <i>"given a time bound, dynamically construct and execute a
problem solving procedure which will (probably) produce a reasonable
answer within (approximately) the time available."</i><p>

If design-to-time is to be generally useful, it must be possible to
embed design-to-time schedulers in larger application systems.  There
are many reasons why a distinct separation should exist between a
design-to-time scheduler and its invoker, including at least
modularity and efficiency.  Modularity suggests that separate
functionality should be kept in separate modules with clearly defined
interfaces.  In general it is difficult for all current problem
solving criteria to be encapsulated into an evaluation function and
transmitted to the scheduler, because deciding what to do is a
evolving computational process.  Another reason why a separation might
exist between a decision maker and a design-to-time scheduler is that
they work at different levels of abstraction.  One of the roles of the
decision maker is to constrain the search done by the design-to-time
scheduler, for example, by using commitments to tell the scheduler
what parts of the task structure to focus on.  While it is possible
for the scheduler to use all available information to make such
decisions itself, for efficiency reasons it is useful to have the
decision maker constrain the search space for the scheduler.  More
details on this aspect of design-to-time scheduling can be found in
our page on <!WA0><a href="http://dis.cs.umass.edu/research/integ.html">integrating scheduling and
decision-making</a>.<p>

To date we have <!WA1><a
href="ftp://ftp.cs.umass.edu/pub/lesser/garvey-dtt-smc.ps">examined
design-to-time scheduling in the Distributed Vehicle Monitoring
Testbed (DVMT)</a>, <!WA2><a
href="ftp://ftp.cs.umass.edu/pub/lesser/garvey-aaai93.ps">looked at
simplified DVMT-like tasks with limited subtask interactions</a>, <!WA3><a
href="ftp://ftp.cs.umass.edu/pub/lesser/garvey-94-08.ps">explored the
interaction between a design-to-time scheduler and a
decision-maker</a>, <!WA4><a
href="ftp://ftp.cs.umass.edu/pub/lesser/garvey-95-03.ps">briefly
described extensions to design-to-time for uncertainty</a>, and
experimented with an optimal design-to-time scheduling algorithm.

<p>
<ul>
<li>Garvey, A., Decker, K., and Lesser, V. <!WA5><a
href="ftp://ftp.cs.umass.edu/pub/lesser/garvey-94-08.ps">"A
Negotiation-based Interface Between a Real-time Scheduler and a
Decision-maker,"</a> UMass CS Technical Report 94-08.

<li>Garvey, A., Humphrey, M., and Lesser, V. <!WA6><a href="ftp://ftp.cs.umass.edu/pub/lesser/garvey-aaai93.ps">"Task Interdependencies in
Design-to-time Real-time Scheduling,"</a> Proceedings of the Eleventh National
Conference on Artificial Intelligence, 1993. 

<li>Garvey, A. and Lesser, V., <!WA7><a href="ftp://ftp.cs.umass.edu/pub/lesser/garvey-dtt-smc.ps">"Design-to-time Real-Time Scheduling,"</a> IEEE
Transactions on Systems, Man and Cybernetics - Special Issue on Planning,
Scheduling and Control, Vol. 23, No. 6, 1993. 

<li>Garvey, A. and Lesser, V. <!WA8><a
href="ftp://ftp.cs.umass.edu/pub/lesser/garvey-95-03.ps">"Design-to-time
Scheduling with Uncertainty,"</a> UMass CS Technical Report 95-03.

<li> Decker, K., Garvey, A., Humphrey, M. and Lesser, V.,<!WA9><a href="ftp://ftp.cs.umass.edu/pub/lesser/decker-91-50.ps">"Real-Time Control of
Approximate Processing,"</a> International Journal of Pattern Recognition and
Artificial Intelligence, Vol 7, No. 2, 1993.

<li> Decker, K., Lesser, V.  and Whitehair, R., <!WA10><a href="ftp://ftp.cs.umass.edu/pub/lesser/decker-89-115.ps">"Extending a Blackboard
Architecture for Approximate Processing,"</a> The Journal of Real-Time Systems, Vol
2, No.  1/2, 1990.
</ul>

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