Richard O. Duda

Use of the Hough transformation to detect lines and curves in pictures

Hough has proposed an interesting and computationally efficient procedure for detecting lines in pictures. This paper points out that the use of angle-radius rather than slope-intercept parameters simplifies the computation further. It also shows how the method can be used for more general curve fitting, and gives alternative interpretations that explain the source of its efficiency.

Subjective bayesian methods for rule-based inference systems

The general problem of drawing inferences from uncertain or incomplete evidence has invited a variety of technical approaches, some mathematically rigorous and some largely informal and intuitive. Most current inference systems in artificial intelligence have emphasized intuitive methods, because the absence of adequate statistical samples forces a reliance on the subjective judgment of human experts. We describe in this paper a subjective Bayesian inference method that realizes some of the advantages of both formal and informal approaches. Of particular interest are the modifications needed to deal with the inconsistencies usually found in collections of subjective statements.

MODEL DESIGN IN THE PROSPECTOR CONSULTANT SYSTEM FOR MINERAL EXPLORATION

Prospector is a computer consultant system intended to aid geologists in evaluating the favorability of an exploration site or region for occurrences of ore deposits of particular types. Knowledge about a particular type of ore deposit is encoded in a computational model representing observable geological features and the relative significance thereof. We describe the form of models in Prospector, focussing on inference networks of geological assertions and the Bayesian propagation formalism used to represent the judgmental reasoning process of the economic geologist who serves as model designer. Following the initial design of a model, simple performance evaluation techniques are used to assess the extent to which the performance of the model reflects faithfully the intent of the model designer. These results identify specific portions of the model that might benefit from “fine tuning”, and establish priorities for such revisions. This description of the Prospector system and the model design process serves to illustrate the process of transferring human expertise about a subjective domain into a mechanical realization.

Pattern Classification by Iteratively Determined Linear and Piecewise Linear Discriminant Functions

This paper describes iterative procedures for determining linear and piecewise linear discriminant functions for multicategory pattern classifiers. While classifiers with the same structure have often been proposed, it is less well known that their parameters can be efficiently determined by simple adjustment procedures. For linear discriminant functions, convergence proofs are given for procedures that are guaranteed to yield error-free solutions on design samples, provided only that such solutions exist. While no similar results are known for piecewise linear discriminant functions, simple procedures are given that have been effective in various experiments. The results of experiments with artificially generated multimodal data and with hand-printed alphanumeric characters are given to show that this approach compares favorably with other classification methods.

Computer Analysis of Moving Polygonal Images

A general mathematical model is developed as an idealization of the problem of determining cloud motions from satellite pictures. The model consists of superimposed planes of rigid moving polygons. The problem is to determine from a sequence of scenes the linear and angular velocities of the figures, and to decompose the scene into its component figures. Study of the model reveals a number of fundamental relations that form the basis for an analysis program. In particular, a systematic anaylsis is given of the topological changes that can occur when overlapping figures move together or apart. A computer program based on these results is described, and experimental results are presented.

Experiments in the recognition of hand-printed text, part II: context analysis

The work described in this paper is part of a larger effort aimed at the recognition of hand-printed text. In a companion paper, Munson describes the scanning of the text, and the preprocessing and tentative classification of individual characters. In this paper, we describe techniques for using context to detect and correct errors in classification.

Experiments with Highleyman's Data

Abstract—The results of three experiments with Highleymans hand-printed characters are reported. Nearest-neighbor classification is used to explain the high error rates (42 to 60 percent) obtained by general statistical procedures. An error rate of 32 percent is obtained by preceding piecewise-linear classification by edge-detecting preprocessing. The minimum human error rate is estimated, and suggested as a performance standard.

SEMANTIC NETWORK REPRESENTATIONS IN RULE-BASED INFERENCE SYSTEMS1

Rule-based inference systems allow judgmental knowledge about a specific problem domain to be represented as a collection of discrete rules. Each rule states that if certain premises are known, then certain conclusions can be inferred. An important design issue concerns the representational form for the premises and conclusions of the rules. We describe a rule-based system that uses a partitioned semantic network representation for the premises and conclusions. Several advantages can be cited for the semantic network representation. The most important of these concern the ability to represent subset and element taxonomic information, the ability to include the same relation in several different premises and conclusions, and the potential for smooth interface with natural language subsystems. This representation is being used in a system currently under development at SRI to aid a geologist in the evaluation of the mineral potential of exploration sites. The principles behind this system and its current implementation are described here.