Documentation

When writing project documents, a top-down breadth-first explanation is easier to understand than a bottom-up one.

The main advantage of the top-down approach is that the document is structured like an upside down tree (root at the top) and the reader can travel down a path she is interested in until she reaches the component she is interested to learn in-depth, without having to read the entire document or understand the whole system.

Technical documents exist to help others understand technical details. Therefore, it is not enough for the documentation to be accurate and comprehensive; it should also be comprehensible.

Here are some tips on writing effective documentation.

• Use plenty of diagrams: It is not enough to explain something in words; complement it with visual illustrations (e.g. a UML diagram).
• Use plenty of examples: When explaining algorithms, show a running example to illustrate each step of the algorithm, in parallel to worded explanations.
• Use simple and direct explanations: Convoluted explanations and fancy words will annoy readers. Avoid long sentences.
• Get rid of statements that do not add value: For example, 'We made sure our system works perfectly' (who didn't?), 'Component X has its own responsibilities' (of course it has!).
• It is not a good idea to have separate sections for each type of artifact, such as 'use cases', 'sequence diagrams', 'activity diagrams', etc. Such a structure, coupled with the indiscriminate inclusion of diagrams without justifying their need, indicates a failure to understand the purpose of documentation. Include diagrams when they are needed to explain something. If you want to provide additional diagrams for completeness' sake, include them in the appendix as a reference.

Aim for 'just enough' developer documentation.

• Writing and maintaining developer documents is an overhead. You should try to minimize that overhead.
• If the readers are developers who will eventually read the code, the documentation should complement the code and should provide only just enough guidance to get started.

Anything that is already clear in the code need not be described in words. Instead, focus on providing higher level information that is not readily visible in the code or comments.

Refrain from duplicating chunks of text. When describing several similar algorithms/designs/APIs, etc., do not simply duplicate large chunks of text. Instead, describe the similarities in one place and emphasize only the differences in other places. It is very annoying to see pages and pages of similar text without any indication as to how they differ from each other.