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
In the walls and mosses If we reach such a very ordinary state of daily life, and then back it up with building and construction that comes from the depths in us, then that gradually accumulates our value in the world, all of us together as a whole. Later, then, perhaps hundreds of years later, people will look back at our stones and say to themselves, "My word, those people way back then — they certainly knew how to live," and they would say this because they could see the lingering whispers in the walls and mosses, and could read them, and could treasure them, and would learn from these traces how to live like that again. Christopher Alexander, The Battle for the Life and Beauty of the Earth From body to body life