Use Case creation elements

Use Case creation elements:

By jefong 2005/04/12

1. the use case is initiated by the system's end user or external environment, and the initiator of the use case is a participant (actor ). The participant may be either a specific person or an external software system.
2. Each use case only describes a separate task, but not multiple tasks. The task described in the use case must be a complete task that conforms to the user's intent. For example, for the software in a bank ATM, "getting money from the ATM" is a task that the user wants to complete, and "entering the password" is only a step in this task.
3. the use case must generate a meaningful result for the user.
4. A well-written use case should have good readability. It consists of multiple sentences, each of which adopts the same syntax (a simple execution step ).
5. the use case view in the UML language can only reflect two types of information:
(1) which participants will interact with our system?
(2) What features do our system need to implement?
6. we should use descriptive text, UML view, or other forms of view to summarize the specific process of an end user to complete a task, determine the sequence of events when the user's operating system software and obtain the expected results.
7. Scenario (scenario) is an execution instance of the use case and an actual path during the execution of the use case. A use case may contain multiple scenarios, such as success or failure.
8. To meet the requirements of the first three elements, use case modeling generally involves the following steps:
(1) determining system boundaries;
The "boundary" of the system is the logical dividing line that separates the functional characteristics of the system from the external environment of the system.
(2) Determine participants;
System boundaries separate systems from participants.
(3) Identify all use cases;
Use Case chart.
(4) determine the level of each case;
Use Case hierarchies. Use Cases include: User target-level use cases, high-level use cases (Summary-level use cases), and sub-function-level use cases. Note: Do not mix the user interface with the user target-level use cases. Each high-level use case can correspond to a software module. sub-function-level use cases have the inclusion and extension relationships.
(5) Write a text description of the use case;
(6) Draw a sequence chart with the entire system as the object;