Instance lines reference classes in the model. If you rename an instance line to another class name that exists in the model, the line acts as a view to the other class in the model. If the class does not exist, IBM® Rational® Rhapsody® will create it.
If you specified analysis mode, the product names the instance line role_n by default and does not prompt you for class information. The following figure shows a new instance line in an analysis sequence diagram.

If you specified design mode, the product names the instance line :class_n by default. If the specified class does not exist, Rational Rhapsody asks if you want to create it. The following figure shows a new instance line in a design sequence diagram.

Classifier role names are animated when their expression can be mapped to an existing object.
Examples:
We have a class A and an object a:A who is the only object of A. All the following names will be mapped to it:
Suppose that instead of a:A, we have a single instance of A as a part itsA of another object b:B.
The instance line can be named as: