A range of different encoding techniques have been developed, along with a number of approaches to applying knowledge. Most of the effort to daze however, has concentrated on representing and manipulating knowledge about a specific domain of application, like game-playing ([14D, natural language understanding ([153, [19]), speech understanding ([8], [II)), chemistry ([7]), etc. This paper explores a number of issues involving representation and use of what we term meta-level knowledge, or knowledge about knowledge'. It begins by defining the term, then exploring a few of its varieties and considering the range of capabilities it makes possible. Four specific examples of meta-level knowledge are described, and a demonstration given of their application to a number of problems, including interactive tranfer of expertise and the "intelligent" use of knowledge. Finally, we consider the long term implications of the concept and its likely impact on the design of large programs.

Crystallographers have been fascinated by computing The problem of deriving the coordinates for a trial devices for many years and have done much pioneering protein structure, given an electron density map, the work in the design and utilization of such devices for amino-acid sequence and the stereochemical principles crystallographic research. Machines such as the 1948 and constraints known to apply, is one which currently analogue Fourier summation device X-RAC (Pepinsky.

C. Richard Johnson, Jr. provided very helpful comments on adaptive control systems. We received many valuable suggestions from members of the Heuristic Programming Project at Stanford. 2 Supported by the Research and Development Branch of the Department of National Defence of Canada.

A candidate elimination algorithm has been shown whicn will find all rule versions consistent with all training instances. Backtracking is not required for noise-free training instances, and the final result is independent of the order of presentation of instances. Version spaces provide at once a compact summary of past training instances and a representation of all plausible rule versions. Pecause they provide an explicit representation for the space of plausible rules, version spaces allow a program to represent "how much it doesn't know" about the correct form of the rule. This suggests the utility of the version space approach to problems such as intelligent selection of training instances and merging sets of independently generated rules.

Computer facilities were provided by t"e SUMEX-AIM facility at Stanford University under National Institutes of health grant RR-00785. The author is supported by the Research and Development Branch of the Department of National Defence of Canada.

Report 77-11 Structure Elucidation Based on Computer S Stanford -- KSL Analysis of High and Low Resolution Mass Spectral Data. A tremendous effort has been directed toward development of advanced instrumentation for mass spectrometrlc analysis. Advancements include everincreasing sensitivities and resolving powers, new ionization techniques, metastable ion probes of ion decomposition and structure and computer systems for rapid acquisition and reduction of data. We sometimes lose sight of the fact that these developments are designed to provide information about chemical and biochemic,a1 structures at greater TeTTE--aTrin greater detail than previously available. The ultimate goal in most research in mass spectrometry is to provide powerful tools for molecular structure elucidation, either directly, by exploitation of existing techniques, or indirectly by development of new techniques. Concurrently, several computer-based techniques designed to assist chemists in the analysis and interpretation of mass spectral data have been developed. Reprinted with permission from Smith, Dennis H. and Carhart, Raymond E. in "High Performance Mass Spectrometry: Chemical Applications," Michael Gross, Ed., in ACS SYMPOSIUM SERIES, No. 70; American Chemical Society: Washington, D.C., 1978, pp.325-347. Library search procedures (2) and their extensions (I) or attern recoviitioz programs (4) may provide clues to t e identity of the structure or be used to determine the structure uniquely. A computer program for analysis of spectra based on classspecific fragmentation rules, is available (5). There are several reasons or this lag: There is no formal theory.

In this paper we examine the selection.

Since the domain expert often knows nothing about programming, the interaction between the expert and the performance program usually requires the mediation of a human programmer.

Both tasks are concerned with the interpretation of large quantities of digitized signal data. The task of SU/X is to understand "continuous signal that is, signals which persist over time. The task of SU/P is to interpret protein x-ray crystallographic data. Some features of the design are: (1) incremental interpretation of data employing many different pattern-invoked sources of knowledge, (2) production rule representation of knowledge, includiR high level strategy knowledge, (3) "opportunistic" hypothesis formation using Dr,

It is generally accepted that problem solving systems require a wealth of domain specific knowledge for effective performance in complex domains. This report takes the view that all domain specific knowledge should be expressed in a knowledge base. With this in mind, the ideas and techniques from problem solving and knowledge base research are reviewed and outstanding problems are identified. Finally, a task domain is characterized in terms of objects, actions, and control/strategy knowledge and suggestions are made for creating a uniform knowledge base management system to be used for knowledge acquisition, DD "" 1473