摘要:

This paper describes an original approach to semantics representation based on the use of a non‐strict functional programming language with polymorphic typing. This approach provides a unified formalism needing no preprocessing or postprocessing to the functional language itself: parsing and semantics are declared naturally using function definition and evaluation is done by lambda application along the lines of Montague. We show that by changing only the model we can, after parsing, compute either the truth value of a sentence or its parse tre

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1993.tb00303.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Recognizing the plan underlying a query aids in the generation of an appropriate response. In this paper, we address the problem of how to generate cooperative responses when the user's plan is ambiguous. We show that it is not always necessary to resolve the ambiguity, and provide a procedure that estimates whether the ambiguity matters to the task of formulating a response. The procedure makes use of the critiquing of possible plans and identifies plans with the same fault. We illustrate the process of critiquing with examples. If the ambiguity does matter, we propose to resolve the ambiguity by entering into a clarification dialogue with the user and provide a procedure that performs this task. Together, these procedures allow a question‐answering system to take advantage of the interactive and collaborative nature of dialogue in order to recognize plans and resolve ambiguity. This work therefore presents a view of generation in advice‐giving contexts which is different from the straightforward model of a passive selection of responses to questions asked by users. We also report on a trial implementation in a course‐advising domain, which provides insights on the practicality of the procedures and directions for future res

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1993.tb00304.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

We investigate the problem of learning two‐layer neural nets ofnonoverlappingperceptrons where each input unit is connected to one and only one hidden unit. We first show that this restricted problem with no overlap at all between the receptive fields of the hidden units is as hard as the general problem (with total overlap) if the learner uses examples only. However, if membership queries are allowed, the restricted problem is indeed easier to solve. We give a learning algorithm that uses examples and membership queries to PAC learn the intersection ofK‐nonoverlapping perceptrons, regardless of whether the instance space in Boolean, discrete, or continuous. An extension of this algorithm is proven to PAC learn two‐layer nets withK‐nonoverlapping perceptrons. The simulations performed indicate that both algorithms are fast and ef

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1993.tb00305.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Bayesian networks provide a natural, concise knowledge representation method for building knowledge‐based systems under uncertainty. We consider domains representable by general but sparse networks and characterized by incremental evidence where the probabilistic knowledge can be captured once and used for multiple cases. Current Bayesian net representations do not consider structure in the domain and lump all variables into ahomogeneousnetwork. In practice, one often directs attention to only part of the network within a period of time; i.e., there is “localization” of queries and evidence. In such case, propagating evidence through a homogeneous network is inefficient since the entire network has to be updated each time. This paper derives reasonable constraints, which can often be easily satisfied, that enable a natural{localization preserving)partition of a domain and its representation by separate Bayesian subnets. The subnets are transformed into a set of permanent junction trees such that evidential reasoning takes place at only one of them at a time; and marginal probabilities obtained are identical to those that would be obtained from the homogeneous network. We show how to swap in a new junction tree, and absorb previously acquired evidence. Although the overall system can be large, computational requirements are governed by the size of one junction

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1993.tb00306.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY