Many time-critical applications, such as emergency response, location-based services, real
time traffic management and environmental monitoring, need instant access to diverse data to
make quick decisions and take instantaneous actions. Imagine the following several scenarios: a
terrorist is bombing an airport near a big city, and mass casualties require immediate medical
response; a serious vehicle incident is happening on a highway, and police need to quickly find
out the incident location for traffic management; a fire is occurring in a residential area, and
fireman have to determine the environmental situation of the residential area right away to
develop suitable rescue strategies; --- All of these scenarios require a rapid, effective and
efficient response. Timely, accurate geographic information from easily accessible databases is
fundamental to the quick response and emergency services dispatch. They are dependent upon
access to complete and up-to-date geographic information from a variety of providers. But it is
often difficult to obtain even basic geographic information promptly. The problem is not
necessarily that the geographic information has not been captured. The problem is accessing and
combinng geographic information from different sources in a timely manner. If the above
situations involve more than one spatial database and these spatial databases are incompatible, it
will be difficult or time-consuming to retrieve the needed geographic information. The issue of
how to acquire data rapidly from different sources and integrate the heterogeneous spatial data
for analysis becomes very important for the time-critical applications where decisions must be
made quickly