Architects have suggested that crime can be prevented by manipulating the design and placement of many simple items, such as doors, bus stops, and park benches. Today's airports prevent crime by replacing bathroom entrance doors with right-angle entrances that permit the warning sounds of crime to travel more freely and that reduce the sense of isolation. Countries throughout the world, such as Australia,Canada,Great Britain, Japan, and the Netherlands have used architectural design techniques to prevent crime. The 2000 Sydney Olympics self-consciously employed architecture to reduce crime by modifying landscapes, restricting access to sites, changing parking patterns,and creating visibility around stadiums.

Unfortunately, for the past six decades, American criminal law has focused on the specific characteristics of offenders (such as economic status, race, age, employment status, and mobility) and has largely ignored the location of crime.20 just as individuals can be recidivists, so too can certain places. Minneapolis,for example, three percent of locations are responsible for fifty percent of calls to which police respond, and similar patterns occur in other cities.

A universal constructor is a machine that can replicate itself and - in addition - make other industrial products. Such a machine would have a number of interesting characteristics, such as being subject to Darwinian evolution, increasing in number exponentially, and being extremely low-cost.

A rapid prototyper is a machine that can manufacture objects directly (usually, though not necessarily, in plastic) under the control of a computer.

The RepRap project is working towards creating a universal constructor by using rapid prototyping, and then giving the results away free under the GNU General Public License to allow other investigators to work on the same idea. We are trying to prove the hypothesis: Rapid prototyping and direct writing technologies are sufficiently versatile to allow them to be used to make a von Neumann Universal Constructor.