A neural network is a way of connecting and programming processors that attempts to simulate the way a human brain works (Neurons are connected through synapses!). Still experimental but used in pattern recognition and learning. They use parallel processing techniques where a number of different processors are performing tasks at the same time, rather than sequential processing where a single processor performs a sequence of tasks one after another.

There are special high level programming languages used for Artificial Intelligence software such as PROLOG and ASPRIN.

An Expert system is a  knowledge-based system that attempts to replace a human 'expert' in a particular field.

An Expert system will consist of

• a large database of knowledge
• facilities for searching the knowledge database
• a set of rules for making deductions from the data (inference engine)

A medical diagnosis  expert system (eg MYCIN) would have information about diseases and their symptoms, the drugs used in treatments etc.

A patient is asked by a doctor about symptoms and the replies are input to the expert system. The computer searches its database, uses its rules and makes suggestions about the disease and its treatments. Sometimes probabilities are assigned to diagnoses.

The computer does not take the place of the doctor but can be used to help the doctor make decisions.

Advantages.

• The computer can store far more information than a human.
• The computer does not 'forget' or make mistakes.
• Data can be kept up-to-date.
• The expert system is always available 24 hours a day and will never 'retire'.
• The system can be used at a distance over a network.

Disadvantages

• Well we don't want to do the experts out of jobs!
• Lacks the 'human touch'!