Administration of Spaces - A Primer of GIS: Fundamental Geographic and Cartographic Concepts - page 239

most significant, development of the SDI occurred in the United States
through the creation of the National Spatial Data Infrastructure (NSDI).
Extending MPLIS concepts to larger geographic regions, the basic prin-
ciple of the SDI is that freer access to administrative GI contributes to good
governance and a better society, government, industry, and people. The
MPLIS provided evidence for the potential; the SDI grapple with the issues
of developing the capabilities of networked data sharing and administrative
coordination that use computer networks to transfer data between different
sites.
Because the NSDI was conceived while the Internet was being devel-
oped, its underlying concepts work without a network; its implementations
explicitly rely on the Internet. The initial goals for the NSDI focused on civil-
ian federal agencies and emphasized the importance of these agencies shar-
ing GI as a means to reduce the expenditures for the federal government.
Although the NSDI was conceived of as guidelines for the development of
infrastructures that reached from federal agencies to local administrations, it
was only sporadically implemented as intended because the NSDI lacked leg-
islation that broadly supported the involvement of local governments or
required the participation of state and local administrations. On this note, it
is important to recognize the inspiration and conceptual guidance the NSDI
has provided administrations in the United States and other countries. While
perhaps not realized as intended, the NSDI has been an important driving
force for improving interoperability.
The NSDI in the United States consists of three components: frame-
work, vertical and horizontal dimensions, and the availability of free or low-
cost data. The framework defines seven data layers needed for nearly every
government activity. This data should provide nationwide coverage. The
framework has both vertical and horizontal dimensions. Vertical refers to
data exchange and sharing between different levels of government; horizontal
refers to the exchange and sharing between administration units at the same
level of government. Finally, the NSDI includes the concept that framework
data should be freely available . Other data can be freely available, or may be
only available after paying a fee or registering with the data provider. This
theoretically allows for the greatest reduction of data collection and mainte-
nance costs by providing support for as many different GI applications as
possible.
Other SDI were developed after the U.S. NSDI was proposed. They
directly incorporated networking capabilities in their design and implemen-
tation. These SDI also are largely developed to support primarily
intragovernmental data exchange and sharing. Public access is generally
quite limited. Most common is to allow access to Internet services that facili-
tate the creation of maps. Some SDI are less integrated in the NSDI. They
offer services to examine descriptive data about available data sets
(metadata) or, after registration, to log on to a protected website and down-
load data.
Free, simple data sharing is the central concept for the SDI, but has
been greatly impaired in every instance by financial and participation issues.