The cloud simulation platform is a broad array of web-based services aimed at allowing users to obtain a wide range of functional capabilities on a "pay-as-you-go" as it is the case of most cloud computing services aimed at making computing services as utilities like water and electricity .
As the Web-based user-interface plays a central role in mediating the physical (real) experiment, section "User-Interface of the cloud simulation" discusses the functionality of the user-interface in addition to various aspects of human-computer interaction, which must be taken into account while developing a user-centered user-interface.
The use-case diagram shown in Figure 3 exposes what takes place in the Windows Azure cloud environment once a user starts the Web-based cloud simulation. As shown in this figure, when the user activates the Web-based cloud simulation homepage, an HTTP request will be sent to the simulator hosted in Windows Azure, which will then ask for username and password for billing issues.
For determining the necessary classes of the cloud simulation, a UML technique designated as Class Responsibility Collaborator analysis (CRC analysis) using cards was applied .
Based on the dynamic of continuous distillation columns, a CRC analysis of the cloud simulation was carried out, in which all the necessary CRC steps were applied.
The workflow of how to start and use a cloud simulation instance hosted in Windows Azure shows Figure 4 consisting of three main steps.
At the end of using the simulation, the user logouts and this leads Windows Azure to terminate the cloud session in a such a way that, on the one hand, the assigned VM machine will be returned to the VM pool, and on the other, it calculates the costs of using the cloud simulation in dependence on time and resources used.