Separate mandatory parts of the use cases from optional parts that can be ordered and delivered separately.
Characteristics: Common. Basic solution.
Keywords: Ordering unit, separating services, system configuration, system version.
Optional Service: Addition pattern contains two use cases and an extend relationship. The first use case models a usage that is compulsory in the system. The second use case models an addition to the first use case that can be added to the system. Because only the additional part is expressed in the second use case, it is abstract; ...