Taxonomy of Learning Systems: Several classification of learning systems are possible based on the above components as follows:
Goal/Task/Target Function:: Prediction: To predict the desired output for a given input based on previous input/output pairs. E.g., to predict the value of a stock given other inputs like market index, interest rates etc.
Categorization: To classify an object into one of several categories based on features of the object. E.g., a robotic vision system to categorize a machine part into one of the categories, spanner, hammer etc based on the parts’ dimension and shape.
Clustering: To organize a group of objects into homogeneous segments. E.g., a satellite image analysis system which groups land areas into forest, urban and water body, for better utilization of natural resources.
Planning: To generate an optimal sequence of actions to solve a particular problem. E.g., an Unmanned Air Vehicle which plans its path to obtain a set of pictures and avoid enemy anti-aircraft guns.
Models:
• Propositional and FOL rules
• Decision trees
• Linear separators
• Neural networks
• Graphical models
• Temporal models like hidden Markov models
Learning Rules: Learning rules are often tied up with the model of learning used. Some common rules are gradient descent, least square error, expectation maximization and margin maximization.
Experiences:
Learning algorithms use experiences in the form of perceptions or perception action pairs to improve their performance. The nature of experiences available varies with applications. Some common situations are described below.
In order to design a learning system the designer has to make the following choices based on the application.