Been rehashing some mmmfs concepts again. I felt a couple of times that "upwards-only" information flow in a tree isn't always enough. For example you can build a web page like that, where every node renders its children in a new context (a list with links, a gallery of pictures etc.) but then nodes can't know their full path. unless you make an exception for paths, which is what I did in mmmfs. That exception was quite costy, i had to spend a week on working around Tup to get that working.