摘要:

Program debugging is an important part of the domain expertise required for intelligent tutoring systems that teach programming languages. This article explores the process by which student programs can be automatically debugged in order to increase the instructional capabilities of these systems. The research presented provides a methodology and implementation for the diagnosis and correction of nontrivial recursive programs. In this approach, recursive programs are debugged by repairing induction proofs in the Boyer‐Moore logic. The induction proofs constructed and debugged assert the computational équivalence of student programs to correct exemplar solutions. Exemplar solutions not only specify correct implementations but also provide correct code to replace buggy student code. Bugs in student code are repaired with heuristics that attempt to minimize the scope of repair.The automated debugging of student code is greatly complicated by the tremendous variability that arises in student solutions to nontrivial tasks. This variability can be coped with, and debugging performance improved, by explicit reasoning about computational semantics during the debugging process. This article supports these claims by discussing the design, implementation, and evaluation ofTalus,an automatic debugger for LISP programs, and by examining related work in automated program debugging.Talus relies on its abilities to reason about computational semantics to perform algorithm recognition, infer code teleology, and to automatically detectandcorrect nonsyntactic errors in student programs written in a restricted, but nontrivial, subset of LISP. Solutions can vary significantly in algorithm, functional decomposition, role of variables, data flow, control flow, values returned by functions, LISP primitives used, and identifiers used. Solutions can consist of multiple functions, each containing multiple bugs. Empiricial evaluation demonstrates that Talus achieves high performance in debugging widely varying student solutions to challenging tas

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1987.tb00169.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Machine instructional planners use changing and uncertain data to incrementally configure plans and control the execution and dynamic refinement of these plans. Current instructional planners cannot adequately plan, replan, and monitor the delivery of instruction. This is due in part to the fact that current instructional planners are incapable of planning in a global context, developing competing plans in parallel, monitoring their planning behavior, and dynamically adapting their control behavior. In response to these and other deficiencies of instructional planners a generic system architecture based on the blackboard model was implemented. This self‐improving instructional planner (SUP) dynamically creates instructional plans, requests execution of these plans, replans, and improves its planning behavior based on a student's responses to tutoring. Global planning was facilitated by explicitly representing decisions about past, current, and future plans on a global data structure called the plan blackboard. Planning in multiple worlds is facilitated by labeling plan decisions by the context in which they were generated. Plan monitoring was implemented as a set of monitoring knowledge sources. The flexible control capability for instructional planner was adapted from the blackboard architecture BB1. The explicit control structure of SUP enabled complex and flexible planning behavior while maintaining a simple planning architectur

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1987.tb00170.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

An increasing number of people are becoming users of unfamiliar software. They can be genuinely “new” computer users or part of a growing group who are transferring skills and knowledge from a familiar product such as a word processor to a functionally similar, but different, unfamiliar one. The problem for users in this position is that they do not have access to training courses to teach them how to use such software and are usually forced to rely on text‐based documentation. LIY is a method for producing computer‐based tutorials to teach the user ofasoftware product.This paper describes how LIY is, in turn, (1) a method for application system design which recognizes the need for tutorial design (a task analysis and user interface specification provide information structures that are passed to the tutorial designer); (2) a support environment for the tutorial designer (in addition to prompting for courseware for nodes in the task analysis, LIY provides a ready‐made rule base for constraining the degree of learner control available while the tutorial is in use. The designer is able to tailor this rule base for a specific tutorial); and (3) a tutorial delivery environment (the tutorial adapts to individual learners and offers a degree of learner

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1987.tb00171.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

This paper compares certain aspects of situation semantics and Montague grammar and points out some issues related to natural language programming. It provides and introduction to certain basic concepts of situation semantics and makes some tentative claims about possible advantages of situation semantics.

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1987.tb00172.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Knowledge representation remains a serious issue for researchers of intelligent tutoring systems. Two areas of knowledge representation that are particularly difficult are domain and teaching knowledge. This article discusses and gives example solutions to these knowledge engineering issues and also addresses issues that relate to up‐scaling existing intelligent tutoring technology to practical levels so that tutoring systems can be brought into the real worl

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1987.tb00173.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

InMinds, Machines,andGödel,Lucas offers an argument, based upon Godel's incompleteness theorems, that his mind cannot be modelled by a machine. This argument has generated a variety of alleged refutations, some of which are incompatible with others. It is argued here that the incompatibility of theserefutationspoints to a puzzle orparadoxwhich has not yet been resolved. A solution to this puzzle is presented in which it is argued that the existence of an algorithm, capable of generating agodel sentencefor an axiomatic model of thatsamealgorithm, is not incompatible with Godels well‐known results. It is further argued that, contrary to received opinion, Gödel's results do not provide grounds for believing that cognitive agents are incapable of proving the consistency of correct formal models of their own cognitive mechanisms. This is shown to be so, even on the assumption that these formal models are known by those agents (onempiricalgrounds) to be formal models of themselves. Finally, the implications of the above issues for theoretical questions in AI are explo

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1987.tb00174.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The major problem with using standard first‐order logic as a basis for knowledge representation systems is its undecidability. A variant of first‐order tautological entailment, a simple version of relevance logic, has been developed that has decidable inference and thus overcomes this problem. However, this logic is too weak for knowledge representation and must be strengthened. One way to strengthen the logic is to create a hybrid logic by adding a terminological reasoner. This must be done with care to retain the decidability of the logic as well as its reasonable semantics. The result, a stronger decidable logic, is used in the design of a hybrid, decidable, logic‐based knowledge representation s

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1987.tb00175.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

A fundamental computational limit on automated reasoning and its effect on knowledge representation is examined. Basically, the problem is that it can be more difficult to reason correctly with one representational language than with another and, moreover, that this difficulty increases dramatically as the expressive power of the language increases. This leads to a tradeoff between the expressiveness of a representational language and its computational tractability. Here we show that this tradeoff can be seen to underlie the differences among a number of existing representational formalisms, in addition to motivating many of the current research issues in knowledge representation.

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1987.tb00176.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Some time ago, McCarthy developed the domain circumscription formalism for closed‐world reasoning. Recently, attention has been directed towards other circumscriptive formalisms. The best known of these, predicate and formula circumscription, cannot be used to produce domain‐closure axioms; nor does it appear likely that the other forms can. Since these axioms are important in deductive database theory (and elsewhere), and since domain circumscription oftencanconjecture these axioms, there is reason to resurrect domain circumscript

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1987.tb00177.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

This paper presents a system of nonmonotonic reasoning with defeasible rules. The advantage of such a system is that many multiple extension problems can be solved without additional explicit knowledge; ordering competing extensions can be done in a natural and defeasible way, via syntactic considerations. The objectives closely resemble Poole's objectives.But the logic is different from Poole's. The most important difference is that this system allows the kind of chaining that many other nonmonotonic systems allow. Also, the form in which the inference system is presented is quite unusual. It mimics an established system of inductive logic, and it treats defeat in the way of the epistemologist‐philosophers.The contributions are both of content and of form: (content) the kinds of defeat that are considered, and (form) the way in which defeat is treated in the rules of inferenc

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1987.tb00178.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY