NGDF Metadata Gateway

Architecture V1.1


5. Distributed Search Interface
NGDF is co-ordinating the establishment of a Gateway to assist the GI industry to locate and access available information. Providers of directory services will be required to register details of their service (address, etc) at a central registry so that the Gateway can provide a link to the relevant services.

NGDF will co-ordinate the distributed network by
  1. maintaining a central register of NGDF endorsed nodes
  2. providing technical support for participatory nodes
  3. providing a quality control measure of the gateway service, by monitoring the availability and performance of the Gateway and the individual distributed directory services and the percentage of successful searches from the Gateway
  4. co-ordinating the establishment of NGDF endorsed replica gateway services
  5. co-ordinate the maintenance of NGDF controlled vocabularies (e.g. keywords)

The NGDF Gateway architecture permits the establishment of multiple gateway interfaces; in fact anyone can establish a gateway to the NGDF service provided they have the details of the distributed directories (metadata index names and Internet addresses). NGDF may manage a gateway interface, itself, may commission and fund the establishment of one or more gateway interfaces or may facilitate the establishment of a number of interfaces. NGDF will co-ordinate the central registry of the directory services and will provide a link to the NGDF Gateway(s) from its Web site.

Other metadata initiatives are investigating the development of gateways to facilitate the location of other information. Where these initiatives (e.g. NBN) use the Z39.50 approach, it will be possible to link the various initiatives and indexes with NGDF. Co-ordination between the relevant bodies (e.g. NGDF and NBN) can ensure that each distributed directory network is available and searchable through the different gateways (where applicable).

The underlying Z39.50 servers can also be accessed by true Z39.50 client software (for further details see http://lcweb.loc.gov/z3950/agency ).

6. Internet Browser
The use of the Internet Web browsers is seen as a standard mechanism for the distribution of information over the Internet and will enable users to search the distributed directories. It will be important for NGDF to ensure that the NGDF search interface is compliant with the common browsers being used. Typically these are the later versions of the Netscape and Internet Explorer browsers.

It is also anticipated that users may have access to local Gateway search interfaces from their desktop. Commercial software offerings may start to provide a local gateway search and MapInfo are currently beta testing such a gateway application that will search GEO profile directories using the central registry list from FGDC. These local gateways mean that users can create a custom interface to search directories of their choice but need access to a central registry list of available databases to ensure they are searching all available indexes.
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