What is Software Architecture? The rules, paradigmen, pattern that help to construct, build and test a serious piece of software. It is the practical experience boiled down to abstract level. Software Architecture builds on System Engineering and the scientific method as established by Galileo Galilei: Measure what you can and make measureable what you can not. The experiment (test) is more important then the deduction. Pieces of information about software architecture are all over the internet. This paper uses citation as much as possible. The aim is to bring together an overview, not to rephrase the wording.