fuzzy logic

In mathematics and computing, a form of knowledge representation suitable for notions (such as ‘hot’ or ‘loud’) that cannot be defined precisely but depend on their context. For example, a jug of water may be described as too hot or too cold, depending on whether it is to be used to wash one's face or to make tea.

The central idea of fuzzy logic is probability of set membership. For instance, referring to someone 175 cm/5 ft 9 in tall, the statement ‘this person is tall’ (or ‘this person is a member of the set of tall people’) might be about 70% true if that person is a man, and about 85% true if that person is a woman.

The term ‘fuzzy logic’ was coined in 1965 by Iranian computer scientist Lofti Zadeh of the University of California at Berkeley, although the core concepts go back to the work of Polish mathematician Jan Lukasiewicz in the 1920s. It was largely ignored in Europe and the USA, but was taken up by Japanese manufacturers in the mid-1980s and was since applied to hundreds of electronic goods and industrial machines. For example, a vacuum cleaner launched in 1992 by Matsushita used fuzzy logic to adjust its sucking power in response to messages from its sensors about the type of dirt on the floor, its distribution, and its depth. Fuzzy logic enables computerized devices to reason more like humans, responding effectively to complex messages from their control panels and sensors.