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
Blessed by the four elements The Indian stone temple also included, in its architectural form, the means for being blessed by the four elements—earth, wind, water, fire. Before entering the temple gates, one removed one's shoes to touch and be blessed by the earth. Then upon passing through the temple gateway, one is blessed by the air with a gust of wind. A blessing by water is obtained by bathing in the temple tank, or at least descending its steps to touch the water. Finally, on entering the cool interior of the sanctuary, the worshipper is given a mark on the forehead with ashes taken from a sacred flame by an attendant priest. Even this blessing by fire has a slight cooling sensation to it. Perhaps it is only coincidental that each of these four blessings is associated with a cooling sensation; and yet, the use of forms and materials that inevitably create coolness is quite remarkable. Lisa Heschong, Thermal Delight in Architecture Avatar: The Last AirbenderThe Legend of KorraA hierarchical system of sense elements