OGC standards play a key
role in SDI
development
OGC Web Services
Most of the Adopted OpenGIS Specifications are for Web-based services. These specifications are collectively called OGC Web Services.
An IBM primer offers a good definition of Web services:
"Web services are self-contained, self-describing, modular applications that can be published, located, and invoked across the Web. Web services perform callable functions that can be anything from a simple request to complicated business processes. Once a Web service is deployed and registered, other applications can discover and invoke deployed service."
The World Wide Web Consortium, OASIS and other standards bodies provide the foundational set of standards that enable services to operate seamlessly within and across enterprise information systems. OGC builds on these basic standards to provide an open standards foundation for geoprocessing services. Recent surveys have shown that many large enterprises - commercial and government - are either using or developing "service-oriented architectures." That is, they are moving to an overall design for their information systems that is based on using Web to provide access to both information and information processing services.
The Web services phenomena grew out of a long-term trend of growing customer demand for interoperability via open standards. Open standards enable interoperability - the ability of different systems to work together. OGC Web Services make it possible for organizations to build geoprocessing into their architectures, to optimize system flexibility, lower integration costs, and improve the ability to insert new technologies.
The OGC Reference Model , the OGC Web Map Service Cookbook , and the Geospatial Portal Reference Architecture were developed to assist the global geospatial technology community in implementing standards-based geospatial solutions that are compatible with Spatial Data Infrastructures in every nation. These documents and others are offered as a resource for rapid development and informed acquisition of portals and applications that can plug and play with geospatial data and services in organizations around the world. NSDI organizations draw from these materials in preparing national and regional SDI policy documents. OGC standards form the foundation for the INSPIRE Geo-Portal in the European Union, the Geospatial One-Stop portal in the US, Australia's Oceans Portal Project, key elements of the Australian Spatial Data Infrastructure (ASDI) and the Canadian Geospatial Data Infrastructure (CGDI), and many other local, state, provincial, regional and national programs.
Below we look at some examples of organizations that are using OGC standards to help them achieve commercial and institutional data sharing objectives.
SDI Implementations
Delivering The British Digital National Framework in GML
In the last several years, the Ordnance Survey, Britain's national mapping agency, has implemented changes that include a simpler pricing and licensing structure; a commitment to e-business and e-delivery; and a complete restructuring of the Ordnance Survey's core digital data. The Ordnance Survey has developed an e-business business model. The Digital National Framework (DNF) is key to the new system, and OGC's Geography Markup Language (GML) is integral. GML is a non-proprietary encoding, based on XML, specifically designed to transfer spatial data over the Internet. During 2000-2001 the Survey's large scale data was transformed from a set of almost 230,000 tiles conforming to a basic, unstructured point and line model to a single, seamless topologically-structured point, line and polygon database. Represented in the database are buildings, roads and paths, administrative boundaries, railways, water features, etc. Users extract data within a particular theme, or group of themes.
Figure 1 shows an example screen-shot of some DNF data, of a small area in the city of Exeter. This image was produced by a viewer that reads GML, extracts the features and renders them according to their attributes (land in green, buildings in sand, roads in grey, etc).
Data Sharing within the United Nations
The UN is a Principal Member of the OGC and has implemented a U.N. Geographic Information Strategic Plan that emphasizes the importance of OGC standards in providing interoperability among the many organizations that make up the UN and that are partners in UN activities. One benefit of WMS is that users can get a raster map of data from a data set whose actual data might be subject to distribution restrictions. That is, the GIS or imaging system that holds the data produces a jpeg or other "simple" image in response to a query from a remote system. Only the simple map image is transmitted, not the vector data or multispectral image data. This simple technical interoperability solution expedites many kinds of institutional cooperation and commercial activity.