Tree structures vs. semi-lattices (and the advantage of organically grown, dynamic structures).

I found the following two paragraphs quite inspiring:

One day in April 2004, Chao Lam sent Mimi Yin a link to an article that he had found in a blog posting by a writer named Clay Shirky, a veteran commentator on the dynamics of online communication. Shirky had written about his rediscovery of an old article by Christopher Alexander, the philosopher-architect whose concept of "patterns" had inspired ferment in the programming world. The 1965 article titled A City Is Not a Tree analyzed the failing of planned communities by observing that typically they have been designed as "tree structures". "Whenever we have a tree structure, it means that within this structure no piece of any unit is ever connected to other units, except through the medium of that unit as a whole. The enormity of this restriction is difficult to grasp. It is a little as though the members of a family were not free to make friends outside the family, except when the family as a whole made a friendship."

Real cities that have grown organically —and real structures of human relationships— are instead laid out as "semi-lattices", in Alexander's terminology. A semi-lattice is a looser structure than a tree; it is still hierarchical to a degree but allows subsets to overlap. Why do architectural designs and planned communities always end up as "tree structures"? Alexander suggests that the semi-lattice is more complex and harder to visualize and that we inevitably gravitate toward the more easily graspable tree. But this "mania every simpleminded person has for putting things with the same name into the same basket" results in urban designs that are artificially constrained and deadening. "When we think in terms of trees, we are trading the humanity and richness of the living city for a conceptual simplicity which benefits only designers, planners, administrators, and developers. Every time a piece of a city is torn out, and a tree made to replace the semi-lattice that was there before, the city takes a further step toward dissociation."

(Rosenberg: pp. 184-185)

Aside from the obvious implications all this has for urban planning, there are also some consequences for software development. In this sense, the traditional approach to programming that viewed it as something akin to building a bridge, a huge work of engineering that needed to be planned way ahead, discussed, negotiated, documented and supervised prior to even laying out the first stone ought to give way to a different, more dynamic approach. This is precisely what has been happening in the last decade or so with the rise of agile methodologies of software development and, in general, the open source approach. Things are now to be understood in a more dynamic manner, as a flow, as something more amorphous, difficult to comprehend and control, an ever-changing set of specifications and features that needs to be managed in the sense of being navigated through —surfed even—, more than controlled. Reality is too rich and diverse to shoehorn it into a predefined shape.

Now, what I find quite interesting in all this is that the above description is quite compatible with the works of Gilles Deleuze, Félix Guattari and Manuel de Landa. Reality is to be described as a rhizome instead of a tree. Hierarchies may exist, but in a completely different form. They are not absolute anymore. They are highly dependent on the position they (and us) occupy in the whole landscape of things. I find it difficult to believe that a philosophy like this may not rise to take center stage in our century, replacing the outdated mechanistic approach of the past.