Foundations and basic concepts
UML: software development and visual modeling

According to the "object paradigm", a system can be seen as a finite set of objects that work together to achieve a global mission. Each object takes part in this collaboration according to a particular behavioral model, which is specified via a class. The principle of classification leads us to consider that two distinct objects governed by the same behavioral model belong to the same class. In the object model, as well as being a means of defining the characteristics and behavior specific to a subset of the system's objects, the class is also a structure dedicated to the creation (instantiation) of objects in this subset.