Recently the demand of the time to use to write use case diagram, where to find some information on record doing software design, especially the needs analysis phase, use case diagram is essential. It is based on user identity system functional analysis, can directly from the user point of view function of the system. In a sense, is a good tool for users to communicate, sometimes can not speak the language to understand things, it is easy to use use-case buttoned.
An overview of use case diagram
1. Use case diagram is known as the participants can observe the external users to the system function model diagram. ("UML Reference Manual")
2. Listed in the system use case diagram use cases and actors outside the system, and shows which players involved in the implementation of which use case (or initiated which use cases).
3. Use Case Diagrams are used for static modeling phase (mainly business modeling and requirements modeling).
Second, use case diagram and explain things
1. Participant (actor)
In the direct interaction with the system outside the system of people or things (such as another computer system or some may be running processes). We need to note:
(1) participants in the role (role) rather than specific people, which represents participants in the process of dealing with the system's role. Therefore, the actual operation of the system, a user may correspond to the actual number of participants in the system. Different users can only correspond to a participant, and thus represent different instances of the same participants.
(2) participants, as external users (not internal) interacts with the system, its main features.
(3) in the following sequence map appears in the "participants", the same with this concept, but the specific meaning to refer to, as the case may be.
2. Use Cases (Use Case)
The system shows a system of external functional unit. Function of the system provided by the system unit, and through a series of system units with one or more messages exchanged between the participants expressed. Create a new use case, confirmed the candidate use cases and classification of the outstanding range of use case law ----" WAVE "test (described later)
3 the relationship between the use case diagram and explanation (where the first to be a notice, I will slowly written all of the following content)
1. Participants and the relationship between use cases - associated with a straight line, said the relationship between actors and use cases occurred, that the use case participants. (Here, no use of maps, added later)
2. The relationship between use cases - including extended
Arrow points to the use case being extended for the use case, called the base use case; arrow starting the use case for extending use case. Extension use case is optional, and if the lack of extension use case does not affect the integrity of the base use case; extended use cases will be implemented only under certain conditions, and its implementation will change the base use case behavior.
Arrow points to the use cases to be included use case, called the included use case; arrow starting the use case as the base use case. Is a must-use case included, if the lack of included use case, the base use case is not complete; contains use cases must be implemented, not have to meet certain conditions; its implementation does not change the basic use case behavior.
3. The relationship between participants - one generalization arrows "Fair party", that is, the father said. Side of origin of the arrow for the "special party", that is sub-square. To inherit particular characteristics of the general side, and added new features.
1 What to do? (Not how to do.)
2 Actor's point of view?
3 Value for the actor?
4 Entire flow of events?
A use case describes the system should do, not what to do.
2 use cases must be based on the participants point of view. (That is, participants should be from the perspective of how to use the system, the definition of use cases, rather than from the perspective of the system itself).
3 Use Case must provide participants with identifiable value.
4 Use cases capture the system and its participants must use the process of a complete flow of events