The most time consuming, and poorly managed part of any GIS system is still the
management and maintenance of core data sets. This takes valuable time and money away
from analysis activities, reducing the overall productivity of the endeavor. The MIT
Urban Information Systems group is taking a fresh look at the way spatial data is
distributed, updated and shared by developing a middle tier of services on top of the
traditional relational database that explicitly separates end-user modifications from
a core, shared data set.

This enables us to imagine systems where different user communities can use the same
core data set, but create different visions of the "truth" by making local
modifications, without breaking the sharing mechanism. If desired, these
modifications can be shared with others, in whole or in part, and new data sets can
be built upon those changes. All this is very "cheap" to implement, as the system
never breaks the ability for the original data set to be synchronized with its source.

The most time consuming, and poorly managed part of any GIS system is still the
management and maintenance of core data sets. This takes valuable time and money away
from analysis activities, reducing the overall productivity of the endeavor. The MIT
Urban Information Systems group is taking a fresh look at the way spatial data is
distributed, updated and shared by developing a middle tier of services on top of the
traditional relational database that explicitly separates end-user modifications from
a core, shared data set. 

This architecture not only allows the core data set to be updated without affecting
third-party changes, but also opens up new possibilities for fine-grained control of
those modifications. Now we can imagine systems where different user communities can
use the same core data set, but create different visions of the "truth" by making
local modifications, without breaking the sharing mechanism. If desired, these
modifications can be shared with others, in whole or in part, and new data sets can
be built upon those changes. All this is very "cheap" to implement, as the system
never breaks the ability for the original data set to be synchronized with its source. 

The system is being licensed under an open source license, and is built upon PostGIS,
MapServer and PHP.