Distributed Geolibraries Spatial Information Resources, Summary of a Workshop (1999) / Chapter Skim
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4 Services and Functions
4 Services and Functions
Pages 53-72
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From page 53... ...
When applied to geospatial data, this remote processing is termed the GIServices mode] to distinguish it from the more traditional local processing of the GISystems model.
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From page 54... ...
Just as today's library needs a catalog that tells users where to look in its stacks for given information resources, so tomorrow's digital library will need the tools (cataloging, indexing, abstracting) that help users navigate the vast communications networks and distributed information resources of the fixture.
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From page 55... ...
A small consulting organization might provide sales services to its clients, payroll and training services for its employees, and marketing or research services to maintain steady growth. The services of a distributed geolibrary fall into several categories, including services for search and retrieval of items of particular interest, item description and display services, dataprocessing services, and services for collection maintenance and growth.
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From page 56... ...
By utilizing the Internet and network communications, a distributed geolibrary could deliver online information services quickly and economically. Agencies and companies can also sell data and recover income more effectively using the Internet's growing and increasingly reliable tools for electronic commerce.
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From page 57... ...
At the mechanic shop, the service known as a tune-up would be comprised of functions such as changing spark plugs, adjusting engine timing or belt alignment, and so forth. Various efforts over the past few years have implemented limited functions of a distributed geolibrary.
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From page 58... ...
Although there are sharp differences in approach and scope, there is now a degree of consensus on the functions that can best deliver the services of a distributed geolibrary. NECESSARY DISTRIBUTED GEOLIBR\RY FUNCTIONS Necessary functions for search and retrieval include searches by geographical location, searches by geographical place name, and searches by secondary requirements such as subject theme or time.
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From page 59... ...
Several suitable sources of data exist for basemaps: · Digital topographic data, available for the entire land area of the planet at i: i,000,000 in the Digital Chart of the World, and for smaller areas at larger scales. For the continental United States the
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From page 60... ...
Search by Place Name Gazetteer is a technical term for an index that links place names to locations. As often found associated with published atlases and city maps, gazetteers provide links to map sheets arid locations within map sheets.
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From page 61... ...
Search by Subject Theme or Time Period In a physical library the card catalog indexes library holdings by subject domain. An electronic catalog may include a thesaurus, which matches synonyms of search topics, providing associations in a search query, for example, between "slough" and "swamp" and "wetland." For cataloging functions to work, items must be stored in a standard format, following an agreed protocol.
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From page 62... ...
Distributed geolibraries should allow their users to narrow specifications of need by including subjects, dates, and other identifying characteristics, as well as needed level of geographic detail, and imposing them on the search in addition to geographic location. Although location is the primary key in searching a distributed geolibrary, other aspects allow the user to limit the number of items of geoinformation identified in a search to reasonable levels.
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From page 63... ...
But the predigital legacy of geospatial data is largely in the form of paper maps and photographic images, which must be laboriously digitized or scanned to be suitable for distributed geolibraries. Although massive investments have been made in
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From page 64... ...
While federal agencies are mandated to create such metadata and have access to extensive resources, there is often little incentive for a local agency to create metadata for its own holdings. Many agencies have suggested simplifications of the FGDC standard; the Alexandria Digital Library (alexandria.ucsb.edu)
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From page 65... ...
In a distributed geolibrary the contents and the users are distributed, and five options can be identified for the catalog: I A unifier!
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From page 66... ...
Search services such as AltaVista and Yahoo build catalogs automatically by usin intelligent agents or web crawlers, but they do so strictly on the basis of words found in text and are not effective ways of building a catalog for a distributed geolibrary. Nonetheless, it may be possible to build a new generation of specialized agents capable of recognizing geoinformation and extracting its important metadata descriptors.
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From page 67... ...
Digital libraries differ from their traditional predecessors in the potential to support extensive manipulation of information once it has been retrieved. This manipulation might include: statistical correction for known distortions; tabulation to obtain statistical summaries; rubber sheeting to register geospatial data sets to known locations or to each other; fonnat conversions, projection changes, and datum changes; · use as input to complex environmental models for purposes of calibration or prediction; · use in complex decision-making processes involving many stakeholders; or generalization, classification, interpretation, and other forms of information abstraction.
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From page 68... ...
2. Search over known or likely sources, using a combination of personal knowledge and the limited capabilities of Internet search services.
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From page 69... ...
The Internet provides limited assistance, and users of the WWW are very much on their own, forced to rely on the limited assistance of online help, manuals, and other devices. If distributed geolibraries are to function as a more powerfi~} evolution of the library model, effective ways must be found to help users navigate through their complexities and ambiguities.
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From page 70... ...
OPTIONS FOR THE DELIVERY OF DISTRIBUTED GEOLIBRARY SERVICES Ideally, we see a distributed geolibrary functioning as a single homogeneous entity capable of responding to a single query from a user, just as AltaVista is capable of responding to a query about some combination of key words. In practice, however, a number of configurations are possible, combining aspects of the following extremes: 1.
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From page 71... ...
This option follows the example of the WWW, for which policies are established by volunteer grassroots organizations that recognize need, devise solutions, and make them freely available to the user community. Protocols and standards allow any individual or group to participate in distributed geolibraries, subject to very loosely defined constraints.
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From page 72... ...
Additional detail can be provided by digital elevation data, so the basemap provides a close resemblance to the actual surface of the Earth. "The role of client and server components should be dynamic and changeable.
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