The problem with trees Many systems are organized hierarchically. The CERNDOC documentation system is an example, as is the Unix file system, and the VMS/HELP system. A tree has the practical advantage of giving every node a unique name. However, it does not allow the system to model the real world. For example, in a hierarchical HELP system such as VMS/HELP, one often gets to a lead on a tree such as: HELP COMPILER SOURCE_FORMAT PRAGMAS DEFAULTS only to find a reference to another leaf: Please see HELP COMPILER COMMAND OPTIONS DEFAULTS PRAGMAS and it is necessary to leave the system and re-enter it. What was needed was a link from one node to another, because in this case the information was not naturally organized into a tree. Tim Berners-Lee, Seeing With Fresh Eyes A City Is Not a Tree hierarchywww
Cool URIs don't change An Essay by Tim Berners-Lee www.w3.org What makes a cool URI? A cool URI is one which does not change. What sorts of URI change? URIs don't change: people change them. The User Interface of URLs www
The blind men who felt the elephant It is so easy to fall into the trap of contemplating a city’s uses one at a time, by categories. Indeed, just this—analysis of cities, use by use—has become a customary planning tactic. The findings on various categories of use are then put together into “broad, overall pictures.” The overall pictures such methods yield are about as useful as the picture assembled by the blind men who felt the elephant and pooled their findings. The elephant lumbered on, oblivious to the notion that he was a leaf, a snake, a wall, tree trunks and a rope all somehow stuck together. Jane Jacobs, The Death and Life of Great American Cities The blind men and the elephantThe group of blind mullahs