[kskz]

This is abstracted and very understandable. The picture is the definition of a function, which in turn invokes the definition of other functions. The P's are abstractions for conditional probability, the sums are loops etc. If this were code, it would be no more than a few lines and very understandable. Unlike code however, for all this there is very thorough documentation for mathematics in millions of pages by thousands of people in many different languages at all levels. The documentation is textbooks, and they're pretty good.