Different levels of use cases

Levels of use cases

• Cloud level. Very high level summary, such as Sell books online. Too high up to be of interest to software development projects, and far too high level to generate code.
• Kite level. Summary level. Again, too high level to be interesting to software development projects and generating code.
• Sea level. People familiar with the Rational Unified Process (RUP) should be familiar with this level of use cases, also referred to as user goal level. A single use case at this level describes a single elementary business process, and realizes a single user (actor) goal. An example could be Place order.
• Fish level. At this level, use cases are often used and re-used as a part of a sea level use case and describe processes that for instance handle selecting a customer, or validating credit cards with a credit card company. This level is also referred to as sub-function level, and includes use cases such as Select product and Pay order. These use cases, including the sea level use cases, are a good head start for generating code that handles the software's behavior.
• Clam level. This is where you hit rock bottom. Use cases at this level should not be defined as use cases, but rather appear as steps in another use case, most likely at fish level. A clear example can be inserting new customers in the database.