UML use case diagram

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

The UML diagram of use cases is widely used indifferent areas, especially where it requires a view of the system in terms of different usage variations or use cases. 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.

The precedent diagram is of great importance forspecifying, 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 for direct design, as well as for a better understanding of their internal design, 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 every 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 onlyare possible, it is best to study from the very beginning. This method will help to 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 a chartA precedent 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.

The contents of the use case in UML modeling are notsays nothing, and the way the diagram is displayed displays all of this. 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 focus on the textual content.

The UML use case diagram, other than the relationshipinclude, 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. This is a waste of effort. After all, it's much more convenient to deal with a text description of a precedent, it is here that the true value of technology is hidden.

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