A number of computer programs have been developed to assist physicians with diagnostic or treatment decisions, and many of them are potentially very useful tools. However, few systems have undergone evaluation by independent experts. The task evaluated was the selection of antimicrobials for cases of acute infectious meningitis before the causative agent was identified. MYCIN was originally developed in the domain of bacteremias and then expanded to include meningitis. Its task is a complicated one; it must decide whether and how to treat a patient, often in the absence of microbiological evidence. It must allow for the possibility that any important piece of information might be unknown or uncertain.

This chapter explores a number of issues involving representation and use of what we term meta-level knowledge, or knowledge about knowledge.1 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 transfer 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. The context of this work is the TEIRESIAS program discussed in Chapter 9. In the earlier chapter we focused on the use of TEIRESIAS for knowledge acquisition. Here we focus on the classification and types of knowledge used by TEIRESIAS. In the most general terms, meta-level knowledge is knowledge about knowledge. Its primary use here is to enable a program to "know what it knows," and to make multiple uses of its knowledge. As mentioned in Chapter 9, the program is not only able to use its knowledge directly, but may also be able to examine it, abstract it, reason about it, or direct its application. This chapter discusses examples of meta-level knowledge classified along two dimensions: (i) specificity character (representation-specific vs. domain-specific), and (ii) source (user-supplied vs. derived). Representation-specific meta-level knowledge involves supplying a program with a store of knowledge dealing with the form of its representations, in particular, their design and organization. Traditionally, this design and organization infor-This chapter is an expanded and edited version of a paper originally appearing in Proceedings of the Fifth IJCAL 1977, pp. Used by permission of International Joint Conferences on Artificial Intelligence, Inc.; copies of the Proceedings are available from William Kaufmann, Inc., 95 First Street, Los Altos, CA 94022. IFollowing standard usage, knowledge about objects and relations in a particular domain will be referred to as object-level knowledge. Type declarations are a small step toward more explicit specification of this information, especially as they are used in extended data types and record structures. As we discuss below, this sort of information, along with a range of other facts about representation design, can be employed quite usefully if it is made explicit and made available to the system.

Performance Level D-RULE578 IF: 1) The infection which requires therapy is meningitis, and 2) Organisms were not seen on the stain of the culture, and 3) The type of the infection is bacterial, and 4) The patient has been seriously burned THEN: There is suggestiv evidence (.5) that pseudomonas-aeruginosa is one of the organisms (other than those seen on cultures or smears) which might be causing the infection UPDATES: COVERFOR USES: (TREATINF ORGSEEN TYPE BURNED) Support Level MECHANISM-FRAME: BODY-INFRACTION.WOUNDS JUSTIFICATION: "For a very brief period of time after a severe burn the surface of the wound is sterile. Shortly thereafter, the area becomes colonized by a mixed flora in which gram-positive organisms predominate. By the 3rd post-burn day this bacterial population becomes dominated by gram-negative organisms. By the 5th day these organisms have invaded tissue well beneath the surface of the burn. The organisms most commonly isolated from burn patients are Pseudomonas, Klebsiella-Enterobacter, Staph., etc. Infection with Pseudomonas is frequently fatal." LITERATURE: MacMillan BG: Ecology of Bacteria Colonizing the Burned Patient Given Topical and System Gentamicin Therapy: a five-year study, J Infect Dis 124:278-286, 1971.

The parser le following paragraphs describe both.

Specifically, one can ask which allows users to solve problems with spoken English a) how might a natural language processor perform commands, has been constructed. The system utilizes a in conjunction with such input devices, and commercially available discrete speech recognizer which requires that each word be followed by approximately a 300 b) how habitable would the resulting voice-interactive millisecond pause. In a test of the system, subjects were able systems be for real users?

Automatic computer programming or automatic programming occurs whenever a machine aids in this process. The amount of automatic programming that is occurring is a variable quantity that depends on how much aid the human is given. There are a number of dimensions on which the level of help can be measured including the level of the language used by the human, the amount of informality allowed, the degree to which the system is told what to do rather than how to do it, and the efficiency of the resulting code. Thus we usually say that there is a higher degree of automatic programming whenever a higher level language is used, less precision is required of the human, the input instructions are more declarative and less procedural, and the quality of the object code is better. The technologies of automatic programming thus include the fields that help move the programming experience along any of these dimensions: algorithm synthesis, programming language research, compiler theory, human factors, and others. This paper will concentrate on only the first of these topics, formal methodologies for the automatic construction of algorithms from fragmentary information. The formal methodologiest have been separated into two categories, synthesis from formal specifications and synthesis from examples. In the former case, it is assumed a specification is given for the target program with adequate domain information so that the target program can be derived in a series of logical steps.

The ability how they can be combined. Thus the user would be to program in natural language instead of traditional taxed more heavily with a natural language system programming languages would enable people to use than with a traditional system. A second argument familiar constructs in expressing their requests, thus against natural language programming relates to its making machines accessible to a wider user group.

Printed in the United States of America PREFACE Among the most challenging scientific questions of our time are the corresponding analytic and synthetic problems: How does the brain function? Can we design a machine which will simulate a brain? Speculation on these problems, which can be traced back many centuries, usually reflects in any period the characteristics of machines then in use. Descartes, in DeBomine, sees the lower animals and, in many of his functions, man as automata. Using analogies drawn from water-clocks, fountains and mechanical devices common to the seventeenth century, he imagined that the nerves transmitted signals by tiny mechanical motions.

Questions are asked and answered every day. Question answering (QA) technology aims to deliver the same facility online. It goes further than the more familiar search based on keywords (as in Google, Yahoo, and other search engines), in attempting to recognize what a question expresses and to respond with an actual answer. First, questions do not often translate into a simple list of keywords. For example, the question (1) Which countries did the pope visit in the 1960s? A much more complex set of keywords is needed in order to get anywhere close to the intended result, and experience shows that people will not learn how to formulate and use such sets. Second, QA takes responsibility for providing answers, rather than a searchable list of links to potentially relevant documents (web pages), highlighted by snippets of text that show how the query matched the documents. While this is not much of a burden when the answer appears in a snippet and further document access is unnecessary, QA technology aims to move this from being an accidental property of search to its focus. In keyword search and in much work to date on QA technology, the information seeking process has been seen as a one-shot affair: the user asks a question, and the system provides a satisfactory response. However, early work on QA (Section 1.1) did not make this assumption, and newly targeted applications are hindered by it: while a user may try to formulate a question whose answer is the information Question Answering 631 they want, they will not know whether they have succeeded until something has been returned for examination. If what is returned is unsatisfactory or, while not the answer, is still of interest, a user needs to be able to ask further questions that are understood in the context of the previous ones. For these target applications, QA must be part of a collaborative search process (Section 3.3). In the rest of this section, we give some historical background on QA systems (Section 1.1), on dialogue systems in which QA has played a significant role (Section 1.2), and on a particular QA task that has been a major driver of the field over the past 8 years (Section 1.3). Section 2 describes the current state of the art in QA systems, organized around the de facto architecture of such systems. Section 3 discusses some current directions in which QA is moving, including the development of interactive QA.

IDijkstra 19591 Dijkstra, E., NA Note on Two Problems in Connection with Graphs," Numeri.scht'