A City Is Not a Tree (1965) [pdf]

This seems to be a very general observation beautifully explained using the example of a city. Human mind likes trees very much because they can be efficiently processed using divide-and-conquer approach. But any tree-like structure used as a description of actual reality runs into its limitations very quickly.

Something to be aware of as a systems designer.

Christopher Alexander also wrote A Pattern Language which was one of the inspirations for Beck and Cunningham's thoughts about software design patterns. Alexander is both an architect and mathematician.

His most recent and probably more important work on the Nature of Order:

http://www.amazon.com/Nature-Order-Phenomenon-Environmental-...

I found the semi-lattice vs tree distinction a very good way of thinking about the systems engineering goal of breaking a project into non-overlapping tasks. The ideal is to get a tree-structure, and not the more complicated semi-lattice.

Making trees out of stuff that isn't naturally a tree complects things. I think regularity and orthogonality trumps a hierarchical decomposition.

HN title-formatting code doesn't properly handle domain abbreviation for .tw TLD

Good catch! Thanks; should be fixed now.