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Chapter 4
Expert System Development Tools

John Durkin


CONTENTS

1. Introduction
2. Historical Overview
3. Types of Tools
3.1. Languages
  3.2. Rule-Based Tools
  3.3. Frame-Based Tools
  3.4. Fuzzy Logic Tools
  3.5. Induction Tools
  3.6. Cased-Based Reasoning Tools
  3.7. Domain-Specific Tools
4. Choosing a Tool
4.1. Knowledge Base
  4.2. Inference and Control Process
  4.3. Explanation Facility
  4.4. Developer Interface
  4.5. User Interface
  4.6. System Interface
  4.7. Hardware
  4.8. Support
  4.9. Cost
  4.10. Ask the Buyers
5. The Tool Market
6. The Future
6.1. Tool Market
  6.2. Integration
  6.3. Domain-Specific Tools
  6.4. Automated Knowledge Acquisition
  6.5. Knowledge Discovery in Databases
  6.6. World Wide Web
References

1. INTRODUCTION

During the past several decades, we have seen expert system technology evolve from a laboratory curiosity into a valuable tool for assisting human decision making. We have witnessed its application over a wide range of tasks: from assisting mine managers with planning mining activities, helping farmers avoid pest infestations, to controlling life support systems aboard the space station. Many reasons can be put forth to help explain this success story, with one of the better ones centered around the introduction and widespread use of expert system development tools called shells. A shell is a programming environment that contains all of the necessary utilities for both developing and running an expert system. Figure 1 shows the architecture of an expert system shell.


FIGURE 1 Expert system shell architecture.

  • Knowledge base contains highly specialized knowledge on the problem area as provided by the expert, and includes problem facts, rules, concepts, and relationships.
  • Inference engine is the knowledge processor, modeled after the expert's reasoning, that works with available information on a given problem, coupled with the knowledge stored in the knowledge base, to draw conclusions or recommendations.
  • Working memory contains the facts entered by the user or inferred by the expert system during a consultation.
  • User interface is the vehicle through which the user views and interacts with the system.
  • Developer interface is the vehicle through which the knowledge engineer develops the system.
  • Explanation facility provides explanations on the reasoning of the system.
  • System interface links the expert system to external programs such as databases, spreadsheets, algorithms, etc., that work in a support role for the system.

We will look at each of these subsystems in more detail later and review some of their more important features to consider when selecting a shell.

In theory, when developing an expert system using a shell, your only major requirement is to place the problem's knowledge in the knowledge base. All the other modules needed to run the system are already there for you. This greatly reduces development time and enables an individual lacking extensive programming experience the opportunity to build the system.

In this chapter we will first look at the history of expert system development tools, including some of the more popular languages. Next we review some of the major types of tools for building knowledge-based systems. We then review the major tool features to consider when selecting a tool, and also look at the results of a survey conducted of expert system developers who were asked to judge the importance of these features. The commercial tool market is also reviewed, where tool sale figures are shown for the last several years. Finally, we consider what the future landscape of the expert system tool market might look like.


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