International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004 
  
NSDI (figure 2). One of the key components of NSDI is the 
National Spatial Data Clearinghouse. OMB (1992) defines the 
National Spatial Data Clearinghouse as an electronic service 
providing access to documented spatial data and metadata from 
distributed data sources. These sources include a network of 
data producers, managers, and users, linked through the Internet 
and other communications means, and accessible through a 
common interface. All spatial data collected by federal agencies 
or their agents, will be made available through the 
Clearinghouse. Spatial data users will have access to the NSDI 
through the National Spatial Data Clearinghouse. 
  
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Figure 2. Components of NSDI. 
One of the very first countries with an NSDI initiative was the 
US. Altough there had been related works before, the US NSDI 
has been officially started in 1994 by the famous executive 
order of Clinton [FR, 1994]. NSDI has gained a great interest 
since then. The NSDI is now a well documented and highly 
active research area. There are plenty of Web sites such as 
FGDC (2004) and CGDI (2004), and numerous studies such as 
MSC (1993) and McLaughlin and Nichols (1994). Furthermore, 
NSDIs are underway in may countries. 
Being the way to interoperability, NSDI is valuable in many 
respects. One On the other hand, NSDI will create new market 
and job opportunities, which is crucial for the countries of a 
high unemployment rate like Turkey. There are many projects 
underway for Canadian Geospatial Data Infrastructure (CGDI, 
2004) and for the US NSDI. And these projects are just for 
building NSDI. There will also be market opportunities and 
projects of high economical and social value which will be 
viable via NSDI. One such project is the new real estate taxation 
system envisioned by Cómert and Akinci (2002). Another one 
is the e-local government which has also been implemented 
(Comert and Akinci, 2003). As already implied, NSDI is a must 
for the recently popular e-government and e-business. NSDI 
will be a major component of e-government. Because, almost 
80 percent of all the information is spatial. Consider the 
involvement of Land Title and Cadastre data for instance. 
3.1.1 A scenario in the current implementation 
Imagine a scenario of generating a Zoning Plan Form (ZPF). 
ZPFs are one the most popular documents since they are the 
3.1 Current NSDI implementations 
Current NSDI implementations can be categorized as either 
"data-cenrtric^ or "human-centric". They are data-centric in 
that they are designed to locate and transfer the desired data. 
They are “human-centric” because they are designed in a way 
that the user controls the workflow. It is not easy, for instance, 
to locate some data from the US Clearinghouse [FGDC, 2004] 
and make it “usable” for a client system. The same is true for 
the Canadian CGDI (Geoconnections, 2004) and United 
Kingdom’s National Geospatial Data Framework (NGDF) 
(Gigateway, 2004). US NSDI has recently initiated Geospatial 
One-Stop, an E-Gov initiative providing access to geospatial 
data and information. GOS was operational in June 2003. 
However even GOS is a “human-centric” implementation. 
Actually, CGDI intents to employ Web services in its 
implementation (CGDI, 2001) and there are around 200 K 
Canadian projects like “smartbroker” (CGDI, 2004) to adopt 
web services. However the services envisioned are rather 
general, they have to be detailed. 
How one carries out his job in a “human-centric” web is 
explained below with the help of a scenario. 
very first step of many activities. For instance, obtaining a 
ZPF is the first step in getting a building permit. ZPFs are 
given by the Zoning Plan Offices (ZPO) of municipalities 
upon the request of the “interested” which might be citizens, 
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