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
It begins with a trip down the stairs The walk from my apartment in Greenwich Village to my studio in Tribeca takes about twenty minutes, depending on the route and on whether I stop for a coffee and the Times. Invariably, though, it begins with a trip down the stairs. The building I live in is a so-called Old Law tenement and was built in 1892, a date inscribed on the metal cornice that also carries the building’s name: Annabel Lee. Like most such tenements, ours is five stories high (a few are six, even seven), and I live with my wife, Joan, on the top floor. Michael Sorkin, 20 Minutes in Manhattan 21. Four-Story Limit