- From: Eliot Christian <echristi@usgs.gov>
- Date: Fri, 22 Feb 2002 11:07:08 -0500
- To: www-zig@w3.org
At 03:55 PM 2/22/2002 +0100, Sebastian Hammer wrote: >[...] What I'd like to consider is whether it would be feasible >to build a structure in which these lists could be merged or >cross-searched... one of the key elements, surely, would be a >good schema for describing targets, second would be some >mechanism for organising a virtual union catalogue (Z39.50, >LDAP, OAI are readily available technologies that come to mind). Such a list of 234 Geospatial Clearinghouse Nodes is maintained at http://clearinghouse4.fgdc.gov/registry/browse.asp?order=title These records are searchable via the GILS Profile as well as the Geospatial Profile. This list can also be regarded as a register of "businesses" that offer "services" over the Web, including but not limited to Z39.50. Viewed in this way, the service metadata is easily modeled in UDDI (Universal Description Discovery and Integration). To show how this works, here's a quick walk-through of the UDDI registrations for geospatial data search services as exposed through distributed UDDI public (and/or private) registries. (The UDDI community home is <http://www.uddi.org/> Go to <http://test.uddi.microsoft.com> and select "Advanced Search". You'll see a pull-down list for ways to constrain your search. Here, choose "tModel by Name" and enter "geo" as the search string. (BTW, a search on "z39.50" also gives interesting results :-) Next, you should see several tModels having names that contain the string "geo". We are interested in the one that looks like this: GEO (Geospatial Metadata) Profile (details) If you were to follow the "details" hyperlink, you would find a description of the Geospatial Metadata Profile and a "discovery URL" pointing to the actual Geo Profile document. (One could, of course, do the same with "Bath", "Bio", ...) Follow the GEO (Geospatial Metadata) Profile hyperlink. This launches a search for all UDDI records that have been described as supporting the Geospatial Metadata Profile service. You will see that there are 234 "business services" supporting the Geospatial Metadata Profile. Each of these correspond to one of the servers in the Clearinghouse noted above. Follow the Alamo Area Council of Governments (AACOG) hyperlink and see business and contact details, as well as "classifications". These classifications can take values from any taxonomy one might want (subject, place, type of library, ...). The classifications and identifiers are the main mechanism by which users discover the businesses and services of interest. In the selected example case, a geospatial "business" offers five "services": Web home page FGDC Entry Point to Geospatial Data Clearinghouse Z39.50 search contents of named database GILS search contents of named database GEO search contents of named database These are all automated services on the Internet. The first two of these are just HTTP Web pages but the last three are all Z39.50 services (unprofiled Z39.50 followed by GILS and Geo Profiles.) This ability to drill down all the way to an automated service is the most innovative part of UDDI. This is where UDDI meets another specification known as Web Service Definition Language (WSD). It is a very useful design feature of UDDI that the business and service metadata chosen by the UDDI community is very similar to what is available via GILS (see <http://www.gils.net/uddi.html> ). This makes it straightforward to construct a two-way GILS/UDDI Gateway. Recntly, the .Net organization within Microsoft began developing just such a gateway, building on a prototype developed by Matthew Dovey. Another interesting wrinkle in the UDDI work concerns the ability to define relationships among businesses. I've published a test view of the top 2000 organizations of the U.S. Federal Government with defined parent-child relationships reflecting their hierarchy. (This data comes from professional catalogers at the University of Illinois-Chicago. Again, this hierarchical classification is easily supplemented with other kinds of classifications so that users have many ways to find the right organization.) To see this in action, go to <http://uddi.rte.microsoft.com/> and choose "search". Select the "Find Provider" tab and enter "U.S. Government".When you click on the "search" button, you'll get results in the left-hand bar. One of those is a hyperlink titled "U.S. Government", described as "National node of an hierarchical taxonomy of government". If you select that hyperlink, the right-hand frame will show the several pieces of that entry (Details, Identifiers, Categories, Discovery URLs, Relationships). If you follow "Relationships", you'll see that "U.S. Government" is the parent of a child entry named "Federal U.S. Government". In this interface, it's pretty tedious to follow the relationship trail. But, if you do you'll find that "Federal U.S. Government" has these six children: Boards, Commissions, and Committees Executive Branch of Federal U.S. Government Independent Establishments and Government Corporations Judicial Branch of Federal U.S. Government Legislative Branch of Federal U.S. Government Quasi-Official Agencies ...and, of course, the chains go quite a bit deeper (ten levels in these top 2000 records). Personally, I believe the UDDI initiative (and similar work in the ebXML community) is exactly what we need for a register of services, including but not limited to those whcih happen to use the z39.50 protocol. Eliot
Received on Friday, 22 February 2002 11:09:28 UTC