UML communication diagram - Ticket processing system

"The most common issue tracking system's design is relatively simple. A database is the main storage repository for all data. The data is managed by the business logic layer of the application. This layer gives the underlying raw data more structure and meaning, preparing it for human consumption. The now human readable data are then presented to the support technician by another software application or web page. The end-user of the issue tracking system can create entirely new issues, read existing issues, add details to existing issues, or resolve an issue. When a user of the system makes a change, the issue tracking system will record the action and who made it, so as to maintain a history of the actions taken. Each user of the system may have issues assigned to them, that is, that user is responsible for the proper resolution of that issue. This is generally presented to the user in a list format. The user may have the option of re-assigning an issue to another user, if needed. For security, an issue tracking system will authenticate its users before allowing access to the systems." [Issue tracking system. Wikipedia]
The UML communication diagram example "Ticket processing system" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Rapid UML solution from the Software Development area of ConceptDraw Solution Park.