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.

  1. ​A City Is Not a Tree​

Tufte: "Some models are supremely better than others: A web of links replaces a hierarchy of nouns, creates a universal architecture for sharing information."