One of the most useful, and most common, type of model is a free-form diagram. Yet they rarely seem to be recognized as an “official” diagram type, perhaps because it’s difficult to set free-form modeling standards or convince you that you need an expensive tool to create them – whiteboards work just fine, thank you. Figure 1 depicts a free-form diagram of the technical architecture for the University system. I regularly see whiteboard drawing like this at clients as well as depicted in architecture books (although these diagrams are usually drawn with a tool such as Microsoft Visio to make them look pretty). This diagram shows the architectural layering, software components such as the business rule and security engines, middleware such as web services and the message bus, and hardware nodes such as the mainframe and application servers. A mishmash of information that would likely require several UML diagrams to capture, UML component diagrams and UML deployment diagrams come to mind, yet this single sketch seems to communicate the architectural landscape for your system nicely.Figure 1. A free-form architecture diagram.
I think the idea of free-form diagrams is self explanatory so I’m not going to go into anymore detail. The important point is to realize that they are a valid architectural modeling option that is available to you.
This artifact description is excerpted from Chapter 10 of The Object Primer 3rd Edition: Agile Model Driven Development with UML 2.