Interoperable spatial data catalogs

The discovery of spatial information on the Web is challenged by the many a pproaches to organizing and presenting it for search. Conventions for searc hing or navigating collections of information on the Web are almost as pers onal and unique as the Web authors who create them. Because there are few r ules in the creation of Internet information sites, and because the number of these sites is increasing exponentially, the discovery of specialized, h ighly structured information - such as spatial information - is especially difficult. Communities that require or generate imagery, cartographic, and thematic spatial data usually manage their information in highly structured ways, but the organizing structures are not standardized. Inventories whos e descriptive content is dynamic are often stored in a database, opaque to systematic web crawler searches. The use of full-text search engines and, e ven more recently, "meta" tags of keywords inside HTML (HyperText Markup La nguage) documents often falls short of imparting the contents of spatial da ta collections. The OpenGIS Consortium (OGC) is in the process of defining implementable, i nteroperable spatial data catalogs that can be used to discover spatial dat a holdings in different data computing environments and across and within i nformation communities. Spatial data catalogs have been around for many yea rs, exemplified by product-specific image catalogs managed by remote sensin g organizations. Unfortunately, there is little interoperability among spat ial data catalogs, requiring the user or agent to traverse and translate ma ny different user interfaces to locate relevant spatial data. In a broadly interoperable environment, a network of generic clients and servers could b e built to enable global discovery of spatial data. As high-level software interfaces are standardized across disparate spatial data collections, acce ss to them may be provided through reasonably lightweight gateway software, building up super-collections across and within information communities de fined by discipline, geography, or cross-discipline interests.