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
But then the knoll was gone These banks were making the same mistake as a family I know who bought an acre in the country on which to build a house. For many years, while they lacked the money to build, they visited the site regularly and picnicked on a knoll, the site’s most attractive feature. They liked so much to visualize themselves as always there, that when they finally built they put the house on the knoll. But then the knoll was gone. Somehow they had not realized they would destroy it and lose it by supplanting it with themselves. Jane Jacobs, The Death and Life of Great American Cities 104. Site Repair