One of the things that I have been pushing for a while is the idea that presentation and content should be separated from one another as best as possible. This has honestly soured me on any form of XML for human-readable document unless it has a very clear set of implementations.<p>This all gets hazy when I discuss archive formats (which, by necessity, have to handle ugly, nasty binary data like JPEGs) but a solidly specified archive format with few interpretations is important.