Part   A part is a property of a classifier and is used to represent the structural composition of a classifier. A part represents a set of instances either owned by the classifier or referenced by the classifier. The instances corresponding to its part may be created when the instance of the containing classifier is created or at some other point in its lifetime. When the containing classifier is destroyed all instances representing the parts are also destroyed. A part can declare a multiplicity, which indicates the allowable number of instances corresponding to the property (part) that can exist within the containing classifier. The multiplicity expression typically follows the name but may be placed in the top right hand corner of the part. Parts may be related to each other using connectors.

Explanation

A part is a property of a classifier and is used to specify the composite structure of a classifier. It has similar meaning to the use of a composition relationship but adds the additional semantics that if two or more parts are connected they must both be owned by the same instance of the containing classifier. When the containing classifier is destroyed all instances representing the parts are also destroyed. Multiplicity expressions can be used to indicate the allowable number of instances that may be created when an instance of the containing classifier is created.