I have been learning UML and have a basic understanding now, but I keep seeing these sort of high level architecture diagrams. Here's one from Microsoft:
Source: A bad picture is worth a thousand long discussions.
Is this a UML diagram? Are there any rules to follow for creating these types of diagrams?
I would like to represent something similar, i.e. the realtionship between different installed systems / APIs... i.e. Platform architecture.
The more appropriate UML diagram to depict a platform's architecture is a component diagram. If you want to go a level lower, then you'd also need to draw one or more package diagrams, and perhaps even a deployment diagram.
The diagram you linked to is not a UML diagram, it's a "marchitecture / marketecture" diagram. It's not really supposed to be technically accurate, its main purpose is to look good on a presentation slide. You can of course chose to go with such a diagram instead of a more formal UML diagram, however there aren't any concrete rules on how to draw them. It should convey a basic idea of your components and how they work together, and... look good ;)
