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The ESTA Directory

Complete description of ESTA

The ESTA directory contains the executable file, full source code, and some implementation examples of the PDC expert system shell ESTA.

Beginning with Visual Prolog version 4.1. ESTA has been reprogrammed, improved and ported to the VPI layer, and supplied with the source code, so that you can modify if to your purposes.

Expert systems are computer systems that mimics the behavior of a human expert in some specific subject area. The idea behind creating an expert system is that it can enable many people to benefit from the knowledge of the expert. Not only will it make specialist knowledge more readily available, but also it may free the expert for the really difficult problems.

By providing it with a knowledge base for a certain subject area, ESTA can be used to create an expert system for that subject:

ESTA + Knowledge Base = Expert System

Each knowledge base contains rules for a specific domain. Thus, for a car fault diagnosis expert system the knowledge base will contain rules relating certain symptoms, such as excessive engine vibrations or lack of power at high speeds to possible causes. Similarly, a knowledge base for an expert system to give tax advice might contain rules relating marital status, mortgage commitments and age to the advisability (from the point of view of legally paying as little tax as possible) of taking out a new life insurance policy, since these sometimes alter an individual's tax position beneficially. And likewise, given a plant classification knowledge base, an expert system could be built to recognize plants.

ESTA has all facilities to write the rules that will make up a knowledge base. Further, ESTA has an inference engine which can use the rules in the knowledge base to determine which advice is to be given to the expert system user or to initiate other actions. ESTA also features the ability for the expert system user to obtain answers to questions such as 'how' and 'why', etc. The separation of the control and inference parts from the knowledge base is a fundamental feature of an expert system shell.

ESTA has context sensitive online-help that describes in all details how ESTA can be used to create an expert system and how to use the created expert system. With the ESTA code you will also find some examples of expertsystems, developed in ESTA, that is in actual use today.