Unified Software Development Process 2: case text writing

What is a use case?
In general, use cases are a set of related success and failure scenarios, which describe how participants use the system to achieve their goals. (defined in RUP: "an instance of a group of use cases, each of which is a series of activities executed by the system, which produce an observed response plant for a participant. ")

Which parts of the case text are included?
Contains the following 13 parts:
Case name: Start with a verb
Scope: systems to be designed
Level: "User target" or "sub-function"
As long as the participant calls the system to deliver the service
Stakeholders and their concerns: Persons who focus on this case and their needs
Preconditions: It is worth telling the reader that the conditions must be true before the start.
Success guarantee: It is worth notifying readers about the conditions that must be met for successful completion.
Main success scenarios: Typical, unconditional, and rational success scenarios
Expansion: an alternative scenario of success or failure
Special requirements: related non-functional requirements
Technology and Data Metadata table: different I/O methods and data formats
Frequency: affects the investigation, testing, and schedule of implementation.
Miscellaneous: for example, unresolved issues
Where
1: its Focus List: This list seems to be more important and practical. It suggests and defines what the system must do. Take the supermarket cash register software as an example.
> CASHIER: It is expected to be accurate and fast, and there is no payment error, because if the payment is received less, it will be deducted from the salary.
> SALESPERSON: The salesperson wants to automatically update the sales commission.
2: condition: convey the noteworthy assumptions that the author thinks should arouse the reader's vigilance.
3: Make sure that the use case must be a real thing after the successful use case is given, including the main success scenario and its alternative path. For example:
> Prerequisites: the cashier must be confirmed and certified.
> Success guarantee: Stores Sales Information, accurately calculates taxes, updates accounting and inventory information, commissions records, and generates bills.
4: main success scenario (Basic Process)
It is also an ideal path, which describes a typical success path that meets the needs of the stakeholders. Note that it generally does not contain any conditions and branches. Although it is not an error to include conditions and branches, it is more understandable and scalable to maintain a certain degree of consistency and extend the processing of all conditions to the extended part.
5: Expansion
Expansion is important and usually occupies most of the text space. The Extension Section describes all other scenarios and branches, including successful and failed paths. Because the extension is the branch of the main scenario, it can be marked by a pair of steps 1... N. For example:
Extension:
3A: Invalid product ID
1. The system prompts an error and rejects the input.
3B :....
An extension consists of two parts: Condition and processing.
Criteria: use conditions that can be detected by the system or participant as much as possible (first), for example:
5A: The system detects communication interruptions with external tax calculation system services
5A: the external tax calculation system is not working properly
The extension can be either for one step or for A series (all). (3-6A) (*)
When an extension point is very complex, you can use a separate use case to express the extension.
Use cases generate branches to execute other use cases (underlined)
6. Special Requirements
Non-functional requirements related to use cases, quality attributes or constraints. these include quality attributes (such as performance, reliability, and availability) that need to be considered and must be included, and design constraints (usually corresponding to I/O devices) such:
Special requirements:
> 90% of credit card authorization responses are less than 30 seconds
> Add pluggable business rules in step 2
7: technology and data metadata table
The variable is about how the system must be implemented. For example
1A "QR scanner or keyboard input product ID
2B: enter credit card account information using a card reader or keyboard
3A :....