Five types of diagrams are used in modeling, and the UML use case diagram is a tool for modeling system dynamic aspects that play a major role in behavior, class, system, and subsystem modeling. Each such diagram has many actors, precedents and relationships between them.
UML use case diagram is widely used in a variety of applications, especially where a view of the system is required in terms of different use cases or use cases. In most cases, this involves modeling the context of a system, class, or subsystem, or modeling the requirements that apply to the behavior of selected elements.
A use case diagram is of great importance for specifying, visualizing and documenting the behavior of a system. Using it, it is easier for the developer to understand the system, subsystem or classes, as well as to look from the outside at the benefits of using elements for a particular context. Such a UML diagram is of particular importance for testing executable systems whendirect engineering, as well as to better understand their internal structure, especially in reverse engineering.
The use case structure is a great tool to find an alternative to the main scenario that leads to success. At each step, ask yourself questions over and over again: “What else can happen?” And in particular: "What can go wrong?" Here it is best to find out from the very beginning all the expansion conditions that are possible. This will help you not to get confused when working on the consequences in the future. All the conditions for solving the problem, which are only possible, are best studied from the very beginning. This method will help you avoid getting bogged down when working on the consequences. Therefore, if possible, consider as many conditions as possible, and this will cause errors to be reduced in the future.
The best option for working with a use case diagram is a graphical table that shows its contents. It is somewhat similar to the context diagram, which is used in structural methods. After all, the table shows the boundaries of the system, as well as its contact with the outside world.
The use case diagram clearly shows the actors, use cases, and relationships between them:
– performance by actors of this or that precedent;
– use cases that include other use cases.
The content of a use case in UML modeling says nothing, but the way the diagram is presented reflects it all. However, you can do without a diagram. Specialistsrecommend that when developing a use case, do not put too much effort into creating a diagram. It will be better if you concentrate on their textual content.
UML use case diagram has other types besides the include relation, for example extend. This is what experts recommend avoiding. The reason lies in the fact that often entire development teams spend a lot of time considering various relationships between use cases. This is a waste of energy. After all, dealing with a textual description of a precedent is much more convenient, this is where the true value of the technology is hidden.
