Supporting Combined Human and Machine Planning:
An Interface for Planning by Analogical Reasoning

Michael T. Cox and Manuela M. Veloso
Computer Science Department. Carnegie Mellon University
Pittsburgh, PA 15213-3891
{mcox;mmv}@cs.cmu.edu


Abstract. Realistic and complex planning situations require a mixed-initiative planning
framework in which human and automated planners interact to mutually construct a
desired plan. Ideally, this joint cooperation has the potential of achieving better plans than
either the human or the machine can create alone. Human planners often take a case-based
approach to planning, relying on their past experience and planning by retrieving and
adapting past planning cases. Planning by analogical reasoning in which generative and
case-based planning are combined, as in Prodigy/Analogy, provides a suitable framework
to study this mixed-initiative integration. However, having a human user engaged in this
planning loop creates a variety of new research questions. The challenges we found creating 
a mixed-initiative planning system fall into three categories: planning paradigms differ
in human and machine planning; visualization of the plan and planning process is a complex, 
but necessary task; and human users range across a spectrum of experience, both
with respect to the planning domaln and the underlying planning technology. This paper
presents our approach to these three problems when designing an interface to incorporate
a human into the process of planning by analogical reasoning with Prodigy/Analogy. The
interface allows the user to follow both generative and case-based planning, it supports
visualization of both plan and the planning rationale, and it addresses the variance in the
experience of the user by allowing the user to control the presentation of information.


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