M. Stefik, Planning and Meta-Planning (MOLGEN: Part 2). Artificial Intelligence 16 (2), 1981.

Author of the summary: J. William Murdock, 1997, murdock@cc.gatech.edu

Cite this paper for:

• Explicit layered representation of knowledge about problem solving provides powerful, flexible reasoning capabilities.

Keywords: Planning, Weak Methods

Systems: MOLGEN; also compares MOLGEN with several other systems: GPS,
TEIRESIAS / MYCIN, HEARSAY like systems such as SU-X, SU-P, and the
Hayes-Roth errand program in [11]). 

Summary: Presents a view of problem solvers as a control hierarchy and
introduces MOLGEN as such a system for planning molecular genetics
experiments.  Argues that task oriented systems in which the
interpreter controls task selection are really just monolithic "black
box" systems since task selection does not use domain knowledge.
Further rejects simple fixes to this problem.  Instead proposes that
knowledge about actions, goals, etc. be explicitly represented in the
same language used to represent the domain knowledge: a meta-level.
Argues for a multi-layered system for handling this sort of knowledge.
Discusses general domain independent heuristics (e.g. "think on the end
before you begin").  Presents MOLGEN as a three level system with the
lowest level being domain space (the actual objects and actions in the
real world), the medium level being the design space (the plan being
developed), and the top level being the strategy space (which mediates
between general heuristics and standard least-commitment planning).
Presents these three layers in detail: the design space possesses a
hierarchy of actions in the world such as cleaving DNA, etc; the
design space posses a hierarchy of operators for manipulating plans
such as computing goal differences, specializing abstract plans, etc.;
and the strategy space has operators that suspend or resume
least-commitment goals, make heuristic guesses, and do backtracking.
Compares MOLGEN with a variety of other systems.  Presents some open
issues.

Summary author's notes:

• This summary came from a file which had the following disclaimer: "The following summaries are the completely unedited and often hastily composed interpretations of a single individual without any sort of systematic or considered review. As such it is very likely that at least some of the following text is incomplete, inadequate, misleading, or simply wrong. One might view this as a very preliminary draft of a survey paper that will probably never be completed. The author disclaims all responsibility for the accuracy or use of this document; this is not an official publication of the Georgia Institute of Technology or the College of Computing thereof, and the opinions expressed here may not even fully match the fully considered opinions of the author much less the general opinions of the aformentioned organizations."