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 ancient fire spirit who lived in the hearth The garden is as central to the concept of an Islamic home as the hearth is to the European home. It is interesting, then, that the hearth-fire in old traditions has a similar association with the life of the inhabitants of the house. Commonly, the fire of the hearth was not allowed to go out. It was carefully covered with ashes each night at curfew so that a few selected embers would survive until morning. (In fact, the word "curfew" originated from the French word for cover-the-fire—couvre-feu.) Raglan comments that "the alarm and horror felt if the hearth-fire went out are out of all proportion to the inconvenience caused" by the need to relight it. Lisa Heschong, Thermal Delight in Architecture Howl's Moving Castle spirit