Expert systems were pretty much the first programs to help people make decisions. One tries to make human knowledge understandable to computers by means of so-called IF-THEN-relationships.

Expert systems were intended for specialists such as doctors, chemists, car mechanics etc. who could support a limited area.

With simple rules such as 

     IF high temperature AND cough THEN a cold
     IF .............................AND ............THEN .................

the special knowledge was collected.

Using a so-called inference motor, a conclusion was drawn from the many IF-THEN controls.

The rules were too "sharp" at the beginning, because what does "high temper or "cough" mean? With 36C I'm healthy and 37C I'm already ill and a cough once is also ill?

Here came alds help the fuzzy logic that could "defuse" soclche IF-DAN formulations and with this "fuzzy" logic we start in the ertsna chapter!