Structures Analysis Expert System

The final aim is to construct a formalized representation of the decision process. Decision trees and structured system analysis are possibilities. Some types of expert systems can derive their own rules from examples. These are described in Chapters 18 and 33. 

In Chapter 43 the incorporation of expertise and experience in data analysis by means of expert systems is described. The knowledge acquisition bottleneck and the brittleness of domain expertise are, however, the major drawbacks in the development of expert systems. This has stimulated research on alternative techniques. Artificial neural networks (ANN) were first developed as a model of the human brain structure. The computerized version turned out to be suitable for performing tasks that are considered to be difficult to solve by classical techniques. 

The evaluation and interpretation of NMR parameters to establish molecular structures is usually a tedious task. An alternative way to elucidate a molecular structure is to directly compare its measured NMR spectrum - serving here as a fingerprint of the investigated molecule - with the corresponding spectra of known compounds. An expert system combining a comprehensive data base of NMR spectra with associated structures, NMR spectra prediction and structure generators not only facilitates this part of the NMR analysis but makes structure elucidation more reliable and efficient. 

Huixiao H, Xinquan X. ESSESA An expert system for structure elucidation from spectra 5. Substructure constraints from analysis of first-order 1H-NMR spectra. I Chem Inf Comput Sci 1994 34 1259-66. 

Huixiao, H. and Xinquan, X., Essessa An Expert System for Elucidation of Structures. 1. Knowledge Base of Infrared Spectra and Analysis and Interpretation Programs, J. Chem. Inf. Comput. Sci., 30, 302, 1990. 

One of the first approaches for expert systems in general was developed by Stanford University at the request of the National Aeronautics and Space Administration (NASA) in 1965 [1]. At that time, NASA was planning to send an unmanned spacecraft to Mars that included a mass spectrometer for the chemical analysis of Martian soil. NASA requested software that would be able to automatically interpret the mass spectra to derive molecular structures. To solve this task, the Stanford team had to encode the expertise of a mass spectroscopist. 

A typical application area of expert systems and their supporting technologies is spectroscopy. Since spectra require interpretation, they are ideally suited for automated analysis with or without the aid of a spectroscopist. Particularly vibrational spectra, like infrared spectra, are subject to interpretation with rules and experience. A series of monographs and correlation tables exist for the interpretation of vibrational spectra [7-10]. The relationship between frequency characteristics and structural features is rather complicated, and the number of known correlations between... 

X-ray phase analysis is used for identification of mineral phases of rocks, soils, clays, or mineral industrial material. The phase analysis of clays is particularly difficult because these materials generally consist of a mixture of different phases, like mixed and individual clay minerals, and associated minerals, such as calcite and quartz. Placon and Drits proposed an expert system for the identification of clays based on x-ray diffraction (XRD) data [45]. This expert system is capable of identifying associated minerals, individual clay minerals, and mixed-layer minerals. It can further approximate structural characterization of the mixed-layer minerals and can perform a structural determination of the mixed-layer minerals by comparison of experimental x-ray diffraction patterns with calculated patterns for different models. The phase analysis is based on the comparison of XRD patterns recorded for three states of the sample dried at room temperature, dried at 350°C, and solvated with ethylene glycol. 

This chapter provides an overview of expert-system verification and validation (V V) techniques. Several methods are presented. First, many of the conventional software V V techniques such as requirements analysis and unit testing can be applied to expert-system development. Second, an expert-system developer can use automated tools to test rule consistency and structure. A more viable alternative, however, is for the developer to create his own set of consistency and completeness tests. Finally, a developer should rely on qualitative judgment to determine the validity of a knowledge base. This judgment could include expert opinion as well as specialized tests designed to determine knowledge-base certification. The chapter suggests that methods should be combined into an optimal mix in order to best undertake V V. 

EXSPEC AN EXPERT SYSTEM FOR STRUCTURE ANALYSIS OF MOLECULES... 

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