11, 1994), established the National Spatial Data Infrastructure (NSDI). He commissioned the Federal Geographic Data Committee (FGDC; chaired by Secretary of the Interior Bruce Babbitt) to document the NSDI, to give it operational form, and to provide a management structure designed to help it grow and become a focus for the combined efforts of both public- and private-sector organizations concerned in any way with the development and use of geospatial information.
In terms of the clear objectives that give it form and sustain it, as well as its highly focused data development and standardization activities, the NSDI is positioned to be a well-defined and vital component of the NII and a valuable resource for those working in a variety of the application areas targeted for intensive development by NII policy planners. However, although the NSDI was conceived as a distributed data resource, it lacks the operational framework to support real-time access to distributed geoprocessing resources and their associated database archives. Resources such as the Wide Area Information Server (WAIS) and Government Information Locator Service (GILS) are available for catalog access and superficial browsing of spatial data sets. But the problem of remote query against the wildly heterogeneous assortment of spatial data sets that constitute the NSDI's ''clearinghouse" environment will not be solved until an operational model for the interoperability of distributed geoprocessing environments is developed and accepted by the geoprocessing community.
The nation's wealth of geospatial data is vast and is used more and more by developers and planners at all levels of operation in both the public and private sectors. Much of the information technology world is rapidly transforming its basis of computation from the tabular domain (the world of spreadsheets and accounting ledgers) to the spatial domain (the world of maps, satellite imagery, and demographic distributions). Applications that merge digital mapping, position determination, and object icons are already being introduced in activities such as overnight delivery service and urban transit. These three technologies and new database management systems capable of handling multidimensional data will play an important role in operations decision support systems, maintenance management, and asset management wherever assets and processes are geographically dispersed.
As the NII concept challenges organizations to adopt more comprehensive, entreprise processing models based on wide-area, multimedia communications technologies, there is a growing need to invest the NSDI with distributed processing capabilities that can ensure the full integration of geoprocessing resources into these models. Commercial need for better spatial data integration is already clear in areas such as electric and gas utilities, rail transport, retailing, property insurance, real estate, precision farming, and airlines. Given the critical nature of applications positioned to combine "real-time" and geospatial attributesemergency response, health and public safety, military command and control, fleet management, environmental monitoringthe need to accomplish the full integration of NSDI resources into the NII context has become increasingly urgent.
Fundamental to the development of enterprise information systems is the concept of interoperability, which is used at all levels of information technology development to define a user's or a device's ability to access a variety of heterogeneous resources by means of a single, unchanging operational interface. At the level of chip technology, the interface is a backplane or a bus specification; at the network level the interface may be a hardware-based transmission protocol or a packet specification; at the operating system level, the interface is a set of system calls or subroutines; and at the object programming level, the interface is a specification for the behavior of object classes. Interoperability thus denotes the user's ability to function uniformly and without product modification in complex environments by applying a standard interface to heterogeneous resources.
In the geodata domain, interoperability is defined as the ability to access multiple, heterogeneous geoprocessing environments (either local or remote) by means of a single, unchanging software interface. Interoperability in this context also refers to accessing both multiple heterogeneous data sets and multiple heterogeneous GIS programs. By definition, this view of interoperability assumes the sort of interoperable network environment envisioned by NII policy.
The interoperability profile of the NII is characterized by multiple hardware and software standards, some complete and some under development. Such standards are the product of years of concentrated effort on the part of both public- and private-sector organizations, as well as such recognized standards bodies as the American