Section 15.7. When to Use a Deployment Diagram

15.7. When to Use a Deployment Diagram

Deployment diagrams are useful at all stages of the design process. When you begin designing a system, you probably know only basic information about the physical layout. For example, if you're building a web application, you may not have decided which hardware to use and probably don't know what your software artifacts are called. But you want to communicate important characteristics of your system, such as the following:

• Your architecture includes a web server, application server, and database.

• Clients can access your application through a browser or through a richer GUI interface.

• The web server is protected with a firewall.

Even at this early stage you can use deployment diagrams to model these characteristics. Figure 15-21 shows a rough sketch of your system. The node names don't have to be precise, and you don't have to specify the communication protocols.

Figure 15-21. A rough sketch of your web application

Deployment diagrams are also useful in later stages of software development. Figure 15-22 shows a detailed deployment diagram specifying a J2EE implementation of the system.

Figure 15-22 is more specific about the hardware types, the communication protocols, and the allocation of software artifacts to nodes. A detailed deployment diagram, such as Figure 15-22, could be used be used as a blueprint for how to install your system.

You can revisit your deployment diagrams throughout the design of your system to refine the rough initial sketches, adding detail as you decide which technologies, communication protocols, and software artifacts will be used. These refined deployment diagrams allow you to express the current view of the physical system layout with the system's stakeholders.

Figure 15-22. You can provide any amount of detail about the physical design of your system