6. Syntactic and structural approaches to classification

The structural approach to pattern recognition considers that the nature of an object to be recognized depends, on the one hand, on the nature of the elementary parts that make it up and, on the other, on the relationships between these different parts.

Structural approaches involve a two-stage strategy. Firstly, the constituent elements of an object are identified using what are usually simple techniques. Then, structural recognition techniques are used to recognize the object (determine its class), represented by its constituent elements and their relationships. We first describe the representations used, then describe two main families of approaches: syntactic methods and structural methods.