Human-Machine Interaction is one of those multi-disciplinary fields that tries to adapt things to the way people work. Whether that’s User Interfaces or physical knobs and levers or design metaphors, the goal is to make the thing more useful. When a command-line interface was the only way to make a desktop computer do useful things, the appeal was limited. Adding a graphical interface to the computer begged the question how do we structure things so people don’t need months of training to use it? Xerox PARC adopted a Desktop metaphor for the graphical environment. Things were structured like your office, with a desk, trashcan, filing cabinets. Email similarly is structured in a format that allowed people to use it without too much training, but it carries with it some legacy design decisions that benefited limitations of the earlier Internet age. Time to shift metaphors I’m afraid.