Jane Jacobs claimed that having multiple Primary Functions was one of her four so called Ingredients Essential to Diversity.

"The district, and indeed as many of its internal parts as possible, must serve more than one primary function; preferably more than two. These must insure the presence of people who go outdoors on different schedules and are in the place fordifferent purposes, but who are able to use many facilities in common." - Jacobs p.150

The essential characteristic of a primary function is that it draws people to an area, rather than caitolizing on or augmenting people's desire to be there for other reasons.


Jacobs is arguing that mixed uses leads to increased diversity and health. Particularly she is saying that designating exclusively corporate, industrial or residential neighborhoods are detrimental to the health of that neighborhood.

Mathematical Form

To formalize her theory we will characterize this quality with a parameter of value between 0 and 1. We will look at zoning and business records to determine primary uses. To simplify the problem we will group uses into catagories. For any given location this parameter will be defined as a function of its proximity to the following catagories of use (Jacobs p161):

  1. Offices and factories
  2. Residences
  3. Education, entertainment, recreation attractions.
  4. Museums, libraries galleries

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