UML use case diagram

Five types of diagrams are used in the simulation, and the UML use case diagram is a tool for modeling system dynamic aspects that play a major role in modeling behavior, class, system, and subsystem. Each such chart has a lot of actors, precedents and relations between them.

The UML diagram of use cases is widely used in various areas, especially where it is required to look at the system from the point of view of different usage variations or precedents. In most cases, it assumes modeling the context of the system, class or subsystem, or simulating the requirements that are imposed on the behavior of the selected elements.

A great importance of the use case diagram is for specifying, visualizing and documenting system behavior. Using it, the developer is easier to understand the system, subsystem or classes, and also to look from the outside to the advantages of using elements for a particular context. Such a UML diagram is of particular importance for testing executable systems in direct design, as well as for a better understanding of their internal device, especially when reverse engineering.

The structure of the precedent is a great tool to look for 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 from the very beginning to find out all the expansion conditions that are possible. This will help in the future not to get confused when working on the consequences.

All the conditions for solving the problem, which are only possible, are best studied from the very beginning. This method will help avoid bogging in the work on the consequences. Therefore, if possible, consider as many conditions as possible, and this will cause a reduction in errors in the future.

The best option for working with the use case diagram is a graphical table that shows its contents. It is somewhat similar to the context diagram used in structural methods. After all, the table shows the boundaries of the system, as well as its contact with the outside world.

The diagram of precedents clearly shows actors, precedents, as well as the relationships between them:

- performance by actors of this or that precedent;

- precedents, including other precedents.

About the contents of the use case in UML modeling does not say anything, and the way the diagram is displayed displays it all. However, you can do without a chart. Experts recommend that when developing a precedent, do not make too much effort to create a diagram. It will be better if you concentrate on the textual content of them.

The UML use case diagram, besides the include relation, has other types, for example extend. It is his specialists who are advised to avoid. The reason lies in the fact that often entire teams of developers spend a lot of time looking at the various relationships between use cases. It's a waste of effort. After all, dealing with the text description of the use case is much more convenient, it is here that the true value of technology is hidden.