Geographical sensors and satellites provide a huge volume of spatial data which is available on the Web. Making use of Web Services, the users are able for provisioning and using these services instead of only for document searching. These services are published in a directory and may be automatically discovered in a given context by software agents. Accessing large digital geographical libraries with geo-spatial information raises some challenges with respect to data semantics, interfaces, data accuracy and updates, distributed processing, as well as with discovery, indexing and integration of geographical information systems; this raise the issue of distributed catalogs forming a federation of spatial databases. Some spatial data infrastructures use service-oriented architecture for accessing these large databases via Web Services.
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