Sharing Geographic Information
Geographic information is inherently distributed and loosely integrated. Rarely can all the necessary information be found in a single database instance with only one data schema. GIS users must often rely on others for GIS data.
The ESRI user community publishes more than 100 million Web maps daily using ArcGIS and ArcIMS applications powered by geodatabases and ArcSDE. Several thousand ArcIMS and ArcGIS Server Web sites deliver standards-based Web services in applications that are distributed worldwide.
GIS portals enable GIS users to publish and discover geographic information so that it can be more easily shared.
This vision has been in existence for more than a decade and is being implemented as NSDIs and GSDIs. A GIS network is an implementation of an SDI that connects users and enables sharing of geographic knowledge via the Web. GIS portals have been established in hundreds of situations including
ESRI is committed to supporting robust GIS portals with functionality for publishing and consuming standards-based Web services in ArcGIS and ArcIMS. ArcGIS provides support for a number of key interoperability initiatives for federated GIS, including the following:
- Metadata. Metadata documents describe the content published at GIS portals. A GIS catalog portal site can also harvest catalogs from a constellation of participating sites so it can reference data holdings contained at other sites. Metadata content standards from the Federal Geographic Data Committee (FGDC), International Organization for Standardization (ISO), European Economic Union (EEU), and other organizations define the standards for how metadata documents record information for GIS datasets and Web services. Each standard is an extension of a general catalog standard such as the Dublin Core.
- XML and Web services. Web services protocols have been developed by OGC, World Wide Web Consortium (W3C), and other organizations. Web services have focused on the use of XML and the definition of specific XML protocols. In the past decade, most organizations have defined their own XML specification. ESRI designed and published the open ArcXML specification. Subsequently, the computing industry has adopted SOAP for XML messaging. OGC has focused on the development of a series of interoperability specifications for GIS on the Web. These include XML specifications for:
- Web Map Service (WMS), which generates map images
- Web Feature Service (WFS), which streams vector features
- Web Coverage Service (WCS) (refers to raster datasets and not traditional ArcInfo coverages)
- Catalog interfaces for the discovery, access, and querying of catalog servers
For more information, visit Open Geospatial Consortium (OGC) at www.opengeospatial.org.
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