Compensating for lack of feedback

In The Death and Life of Great American Cities, Jane Jacobs writes that very successful neighborhoods can destroy themselves. In short, what happens is that the diversity of a successful neighborhood decreases, or monotony increases. Diversity, writes Jacobs, is one of the fundamental factors for successful neighborhoods, districts, and cities. Big companies, most notably banks and insurance companies, are attracted to already successful areas, taking over spaces occupied by smaller businesses, lower-rent residences, et cetera.

As the concentration of offices increase, the number of people using the neighborhood at other times than office hours decrease. Jacobs writes about lower Manhattan, which at the time she wrote the book was troubled by self-destructing diversity. She notes that the reason that shops and restaurants had to move out, was that they were too small to serve the hoards of people coming there at daytime, and too big to survive outside office hours, when the area was largely deserted.

Jacobs suggests that successful neighborhoods should be thought of as lacking feedback regulation. In other words, successful neighborhoods can’t adapt; they can’t regulate themselves to maintain the diversity that makes them successful. “I doubt that we can provide for cities anything equivalent to a true feedback system,” she writes, “working automatically and with perfection. But I think we can accomplish much with imperfect substitutes.”

These imperfect substitutes are: “zoning for diversity; staunchness of public buildings; and competitive diversion.” First I thought that this was about compensating for lack of feedback with control, but as I thought more about it, I realized that it was actually more about indirect influence; about applying measures to help neighborhoods maintain diversity.

Zoning for diversity means using taxes, imposing height or age limitations, et cetera – basically to keep old buildings from being knocked down in favor of tall buildings that decrease diversity. A height limitation, for instance, makes it no longer worthwhile to tear down an old building, since a new building can’t be tall enough to generate return of investment. Tax regulations also serve this purpose, whether it implies higher taxes for new buildings, or reduced taxes for old ones.

Staunchness of public buildings is about placing (or keeping) public buildings in places where they increase (or maintain) diversity. She mentions Carnegie Hall, which apparently was planned to be replaced by office buildings, but which was bought by “a quasi-public body”. Carnegie Hall makes the neighborhood attractive to people, and creates a stream of people visiting bars and restaurants nearby.

Competitive diversion means stimulating the four fundamental factors for successful neighborhoods: primary mixed uses (a balance of businesses, residences, shopping, etc); small blocks (different paths to navigate through neighborhoods, ensuring that neighborhoods are weaved together); aged buildings (too expensive space results in monotony); concentration (a certain concentration of uses is needed to make the neighborhood function well).

Had cities been capable of regulating themselves using feedback, this indirect controlling, or influencing, wouldn’t be necessary. This compensating for lack of feedback seems relevant for software architecture. I haven’t yet quite figured out how, though.

The above was posted to my personal weblog on April 2, 2003. My name is Peter Lindberg and I am a thirtysomething software developer and dad living in Stockholm, Sweden. Here, you’ll find posts in English and Swedish about whatever happens to interest me for the moment.

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