CEOS IDN Archives Scenario

Steve Foley
20 February 1996

This provides a comparative study between existing archiving practices and the Reference Model (RM) produced by Lou Reich. The specific scenario detailed is the International Directory Network (IDN) of CEOS.

The CEOS IDN is based around a database generated from descriptions of data holdings held by organisations around the world. Researchers can input search queries using a user interface on the World Wide Web (URL: ). This database, known as the Global Change Master Directory (GCMD), allows researchers to inquire about relevant data sets addressing a specific need. As a database, the GCMD does not qualify as a valid scenario to use in assessment of the RM. It is merely designed to assist researchers in locating information useful to their study.

The central aspect of the GCMD database is the high-level data set descriptions that give the user basic information on the data, and a point of contact if they wish to pursue the inquiry further. Each description, in ASCII-text format, is labelled Directory Interchange Format (DIF) and contains as much information as is sensibly possible about the holding from the data provider. The GCMD is updated regularly to ensure researchers have access to relevant information on data holdings.

Where some relevance to the RM may be found is in the "Metadata Management" Service Module. One input into this module is "Populate Metadata", and it is this function that DIF generation assumes. The DIFs that constitute the GCMD can be regarded as Metadata descriptions of data, although the IDN offers no facility to proceed to browse catalogues of data held at specific data centres, or to receive browse imagery and the like. The purpose of the CEOS IDN is simply to make researchers aware of data that is out there which may be of relevance to their work.

DIFs contain a number of fields which may or may not be completed. The major fields include start/stop dates, spacecraft/sensor, investigator, data contact, storage medium, parameters measured and derived, discipline, location, geographic coverage, general keywords, summary, and data quality. Some fields such as parameter keywords, discipline, data centre, and sensors are "controlled" fields on the user query page. This limits the entries possible in these fields and helps to locate appropriate data descriptions for the researcher's request.

In conclusion, the CEOS IDN utilises a database of data descriptions (DIFs) generated by data providers which advertise their data holdings. Due to its database quality it is considered inappropriate as a worthy comparative for the RM or archive definition.

Steve Foley

FarnboroughHampshire GU14 6TD
Tel: +44 (0) 1252 393252
Fax: +44 (0) 1252 522959

Wider Views

Overview of the First International Workshop
Overview of International Effort


A service of NOST at NSSDC.

Author: Steve Foley ( +44.0.1252.393252
Curator: John Garrett ( +1.301.441.4169
Responsible Official: Code 633.2 / Don Sawyer ( +1.301.286.2748
Last Revised: 20 February 1996, Steve Foley (14 April 1998, John Garrett)