Pattern recognition system based on empirical knowledge: Sandalwood and camphoraceous odours application

In the first part of this paper, structure–odour relationships for sandalwood odourants were studied for a set of 158 compounds (75 inactive and 83 active). The first step in the study consists in an evaluation of empirical rules concerning structure–sandalwood odour relationships, by means of decision trees. The main structural elements responsible for other than sandalwood odours are defined from the empirical rules. A search for new variables was carried out to define the essential elements for the sandalwood odour. The rules used to discriminate between sandalwood and non-sandalwood molecules lead to 80% correct discrimination. In the second part, fuzzy logic has been used as a tool in structure–camphoraceous odour relationships. The database studied included 99 molecules. The rules used to discriminate between camphor and non-camphor are given by an expert. Such rules account for the shape and the size of the molecules. Their adjustment by means of genetic algorithms (GAs) lead to 84% correct discrimination between camphor and non-camphor molecules.