When writing cases, many people can't understand the concept of expansion and extension, I have also been a headache for this time. After a period of exploration, I understand, so I wrote this essay with everyone.
Use cases can extend (extend) an existing case. In the extended case, the extension occurs on a specific point, called an Extension Point. Extensions can be regarded as inserting additional description text in an extension in an extension point in a particular case. Extensions are mainly used to simplify complex event streams to represent alternative behavior or processing exceptions. Using extended modeling makes basic use cases easier to understand, and the usage model is easier to maintain. (Excernation "P83) Based on" Unified Software Development Process "P83) Next is an example of use of extended points (taken from" effective use case mode "P186 ~ 187): Use Example 7.5" Booking flight "booking flight 1. When the agent specifies the customer When traveling routes, use the case to start. 2. The system searches a set of qualified flights and provides them with the agent. (Flying Flight A) 3. The agent chooses "Choose flight." 4. System Verify that there is also a seat on the flight and remember the seat. (Flying Flight B) 5. The agent provides payment information and ends your reservation. (Flying Flight C) 6. The system reserves the seat and passes the ticket. The branch 4A does not have a seat in the selected ticket class to provide: 4A1. System notification agent, no seats can be provided in the fare category selected by the customer. 4A2. Agent designated another price preference. 4B No seats can be provided (full): 4b1. The system notification agent does not have a seat. 4b2. The agent specifies the time preference of another group of customers. (Flight History D)
Example 7.6 "Booking for Flying Flight" Use examples to expand the "Booking Flight" to the Flights Flight A 1. The system retrieves the customer's information, and displays a flight according to customer's route preferences. Flying frequent visits B 1. The system provides customers with heads. Flying frequent visits C. System Verify that customers have upgraded coupons in their accounts 2. The system is included in the flight upgrade list. The branch has no seats to provide flying frequent visits D 1. Agent puts the customer on a seat waiting list.
RUP embodiment statute (Use Case Specification) while having alternative flow template (Alternative Flows) and extension points (Extension Points), as follows: 2.2 Alternative Flows 2.2.1 [More complex alternatives should be described in a separate section, which is referred to in the Basic Flow subsection of Flow of Events section. Think of the Alternative Flow subsections like alternative behavior-each alternative flow represents alternative behavior, many times because of exceptions that occur in the main flow. They may be as long as necessary to describe the events associated with the alternative behavior. When an alternative flow ends, the events of the main flow of events are resumed unless otherwise stated.] 2.2.1.1 [Alternative flows may, in turn, be broken down into subsections if it improves clarity.] 2.2.2 [There may be, and most likely will be, a number of alternative flows in a use case. Keep each alternative separate to improve clarity. USING Al ternative flows improves the readability of the use case, as well as preventing use cases from being decomposed into hierarchies of use cases. Keep in mind that use cases are just textual descriptions, and their main purpose is to document the behavior of a system in a Clear, Concise, and UndAndable Way.
6. EXTENSION POINTS [EXTENSION POINTS OF THE USE.] 6.1 [definition of the location of the extension point in the flow of events.] According to the definition of the extension and extension points given above, Demonstration, it is not difficult to know that the branch of the application example demonstration in the RUP template is a centralized description of the expansion point in the example exemplary. According to Template Note We can rewrote the use examples: Use Example 7.5 "Booking Flight" Subscription Flight 1. When the agent specifies the travel route for the customer, use the case to start. 2. The system searches a set of qualified flights and provides them with the agent. 3. The agent chooses "Select flight". 4. System Verify that there is also a seat on the flight and remember the seat. 5. The agent provides payment information to end the reservation. 6. The system reserves the seat and passes the ticket. Alternative stream 4A does not have a seat in the selected ticket class to provide: 4A1. System notification agent, no seats can be provided in the fare category selected by the customer. 4A2. Agent designated another price preference. 4B No seats can be provided (full): 4b1. The system notification agent does not have a seat. 4b2. The agent specifies the time preference of another group of customers. Extension 1.46 "Booking for Flights" is required to note that there must be an extension with an extension. In summary, alternative flow and extension points are used to represent alternative behavior or processing exceptions, and in some case description templates, they are put together, and they separate them in the RUP template. Why is it separate? The reason is that expansion is different from an alternative behavior or processing exception to the exception. When the branch action path interrupts a large number of steps in a scenario, creating an extension is suitable, which is the interruptasextension model mode.
