Environment, Learning classifier

The CS comes into its own when the rules that are needed to control the environment are only partly known, or are completely unknown, so that a comprehensive set of ES rules cannot be constructed by hand. If we cannot create the ES by hand, it must also be impossible to create the CS by hand some other method of creating the classifiers must be found. This is the realm of the learning classifier system (LCS) in which all classifier systems of value lie. 

Classifier systems are software tools that can learn to control or interpret complex environments without help from the user. This is the sort of task to which artificial neural networks are often applied, but both the internal structure of a classifier system and the way that it learns are very different from those of a neural network. The "environment" that the classifier system attempts to learn about might be a physical entity, such as a biochemical fer-mentor, or it might be something less palpable, such as a scientific database or a library of scientific papers. 

As we shall see in this chapter, the classifier system is given no advance knowledge to help it plan what to do. Data on the chemical reactions that may be occurring or the values of rate constants are not provided therefore, it is wholly dependent for its success upon learning, which it manages by investigating the environment. This is a very different approach from one that relies on a comprehensive theoretical model of the reactions in the system. 

After many cycles, productive classifiers will have gained significant strength, but those classifiers that are not of value in controlling the environment will have accumulated little. The reward scheme thus allows us to identify the more useful classifiers, but how can we persuade the system as a whole to learn ... 

The rates of many enzyme reactions are strongly dependent on both pH and temperature. Construct a CS that learns to keep conditions within a simple reactor within the limits 6 < pH < 9 and 27 < T < 41. You will need both to write the classifier system itself and a small routine that represents the environment. Test the operation of your system by including a method that periodically adds a random amount of acid or base, or turns on a heater or chiller for a short period. 

---