[webkit-dev] Documenting common null pointer errors

In reviewing patches, I feel like I'm commonly pointing out DOMWindow::frame and Document::frame, etc, can be null in some circumstances. Would it be useful to have a diagram of the major objects (Page, Frame, DOMWindow, Document, etc) somewhere on webkit.org that shows their relation, which links can be null, and which objects change / are preserved during navigation? If so, I'm happy to create this with my current knowledge, and hopefully folks with more experience will add parts that I don't know. What's the best medium to make this easy to update in the future? SVG? ASCII art? Adam