摘要:

The Coach system, a computer simulation of a human tutor, was constructed with the goal of obtaining a better understanding of how a tutor interprets the student's behavior, diagnoses difficulties, and gives advice. Coach gives advice to a student who is learning a simple computer programming language. Its intelligence is based on a hierarchy of active schemas that represent the tutor's general concepts and on more specific information represented in a semantic network. The coordination of conceptually guided and data‐driven processing enables the Coach system to interpret student behavior, recognize errors, and give advice to the studen

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1986.tb00076.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The focus of this paper is on the underlying knowledge base for an intelligent tutorial system for high‐school algebra problems. We present a model of problem solving flexible enough to account for a variety of problem‐solving behaviors and general enough to allow new problem domains to be defined easily. The model is based upon the analysis of protocols between students and expert tutors. We show how student errors can be monitored and remediated using the model, and we provide an approach to understanding problem difficulty that can be used to generate challenging problems and also provides a mechanism for planning their solut

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1986.tb00077.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

This paper describes an object recognition algorithm both on a sequential machine and on a single instruction multiple data (SIMD) parallel processor such as the MIT connection machine. The problem, in the way it is presently formulated on a sequential machine, is essentially a propagation of constraints through a tree of possibilities in an attempt to prune the tree to a small number of leaves. The tree can become excessively large, however, and so implementations on massively parallel machines are sought in order to speed up the problem. Two fast parallel algorithms are described here, a static algorithm and a dynamic algorithm. The static algorithm reformulates the problem by assigning every leaf in the completely expanded unpruned tree to a separate processor in the connection machine. Then pruning is done in nearly constant time by broadcasting constraints to the entire SIMD array. This parallel version is shown to run three to four orders of magnitude faster than the sequential version. For large recognition problems which would exceed the capacity of the machine, a dynamic algorithm is described which performs a series of loading and pruning steps, dynamically allocating and deallocating processors through the use of the connection machine's global router communications mechanism.

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1986.tb00078.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

We describe a shell for expert systems written in Prolog. The shell provides a consultation environment and a range of explanation capabilities. The design of the shell is modular, making it very easy to extend the shell with extra features required by a particular expert system. The novelty of the shell is twofold. Firstly, it has a uniform design consisting of an integrated collection of meta‐interpreters. Secondly, there is a new approach for explaining ‘why not,’ when a query to the system

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1986.tb00079.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The primary goal of this paper is to illustrate how smaller deductive search spaces can be obtained by extending a logical language with restricted quantification and tailoring an inference system to this extension. The illustration examines the search spaces for a bottom‐up parse of a sentence with a series of four strongly equivalent grammars. The grammars are stated in logical languages of increasing expressiveness, each restatement resulting in a more concise grammar and a smaller search space.A secondary goal is to point out an area where further research could yield results useful to the design of efficient parsers, particularly for grammatical formalisms that rely heavily on feature system

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1986.tb00080.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Problem solvers that use heuristics to guide choices often run into untenable situations that can be characterized as overconstrained. When this happens, the problem must be able to identify the right culprit from among its heuristic choices in order to avoid a potentially explosive search. In this paper, we present a solution to this for a certain class of problems where the justifications associated withchoice pointsinvolve an explicit assessment of the pros and cons of choosing each alternative relative to its competitors. We have designed a problem solver that accumulates such knowledge about the pros and cons of alternative selections at choice points during heuristic search, which it updates in light of an evolving problem situation. Whenever untenable situations arise, this preserved knowledge is used to determine the most appropriate backtracking point. By endowing the backtracker with access to this domain‐specific knowledge, a highly contextual approach to reasoning in backtracking situations can be achieve

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1986.tb00081.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

We are concerned with developing a computational method for selecting possible antecedents of referring expressions over sentence boundaries. Our stratified model which uses a Λ‐categorial language for meaning representation incorporates valuable features of Fregean‐type semantics (a la Lewis, Montague, Partee, and others) along with features of situation semantics developed by Barwise and Perry. We consider a series of selectedtwo‐sentence storieswhich we use to illustrate referential interdependencies between sentences. We explain the conditions under which such dependencies arise, explain the conditions under which various translations can be performed, and formalize a set of rules which specify how tocomputethe reference. We restrict our discussion to two‐sentence stories to avoid most of the problems inherent inwhere to look for the reference,that is, how to determine theproperantecedent. We restrict our considerations in this paper to situations where a reference, if it can be computed at all, has a unique antecedent. Thus we consider examples such asJohn wants to catch a fish. He (John) wants to eat it.andJohn interviewed a man. The man killed him (John).We then summarize the transformation which encompasses these rules and relate it to the stratified model. We discuss three aspects of this transformation that merit special attention from the computational viewpoint and summarize the contributions we have made. We also discuss the computational characteristics of the stratified model in general and present our ideas for a computer realization; there is no implementation of thet“ratified model at

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1986.tb00082.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Default reasoning is analyzed as consisting (implicitly) of at least three further aspects–oracles, jumps, and fixes‐which in turn are related to the notion of a belief. Beliefs are then discussed in terms of their use in a reasoning agent. Next an idea of Israel is embellished to show that certain desiderata regarding these aspects of default reasoning lead to inconsistent belief sets, and that as a consequence the handling of inconsistencies must be taken as central to commonsense reasoning. Finally, these results are applied to standard cases of default reasoning formalisms in the literature (circumscription, default logic, and nonmonotonic logic), where it turns out that even weaker hypotheses lead to failure to achieve commonsense default conclusi

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1986.tb00083.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The input to the described program, in learning mode, consists of examples of starting graph and result graph pairs. The starting graph is transformable into the result graph by adding or deleting certain edges and vertices. The essential common features of the starting graphs are stored together with specifications of the edges and vertices to be deleted or added. This latter information is obtained by mapping each starting graph onto the corresponding result graph. On subsequent input of similar starting graphs without a result graph, the program, in performance mode, recognizes the characterizing set of features in the starting graph and can perform the proper transformation on the starting graph to obtain the corresponding result graph. The program also adds the production to its source code so that after recompilation it is permanently endowed with the new production. If any feature which lacks the property “ordinary” is discovered in the starting graph and only one example has been given, then there is feedback to the user including a request for more examples to ascertain whether the extraordinary property is a necessary part of the situat

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1986.tb00084.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY