Volume 14, Number 1, March 1998
By John Garrett, Donald Sawyer, and Robert Stephens

Update on Data Entity Dictionary Standards

In t he previous issue of this newsletter, we described the status of the international space agency developed Data Entity Dictionary Specification Language (DEDSL) draft standard. This is being developed under the Consultative Committee for Space Data Systems (CCSDS) and ISO TC 20/SC 13. We reported on the need to harmonize this work with the existing ISO standards addressing data element standardization and designated ISO 11179. In this issue we describe the current status of this work as well as developments related to ISO 11179.

The development of ISO 11179 has been led by individuals from various organizations and agencies in the Washington D.C. area. They have recognized that ISO 11179 contains ambiguities and therefore, under ANSI NCITS L8 (formerly ANSI X3L8), they have developed a formally specificied model designated ANSI X3-285 and titled Metamodel for the Management of Shareable Data. Central to this model is the concept of a metadata registry which assigns unique identifiers to each data element. The objective is to make the definitions and representations of the data elements widely understandable and re-usable.

Several organizations have begun implementing these metadata registries. The Environmental Protection Agency, which has been an active supporter of ISO 11179, has established such a registry and it is being promoted as a reference implementation of ISO 11179 under ANSI X3-285. Further, a second metadata registry workshop, to be held in the Washington D.C. area, is planned for April 15-16 to educate implementors and address issues. One of the issues is the lack of a standard concrete syntax for the exchange of data element definitions. The emerging internet XML and RDF standards have been proposed as candidates for this function. Participation from the Space agencies has been solicited due to our experience in developing and using PVL/ODL for Data Entity Dictionary expression.

From the CCSDS perspective, the current objective is to produce a DEDSL standard that is harmonized with ISO 11179 and ANSI X3-285, and that will be understandable and usable to agency science and operations disciplines in the near term. Its concrete syntax is PVL based.

From a NASA perspective, NOST would like to form a Data Entity Dictionary Interest Group to track and influence standards development, and to facilitate broader and more effective NASA Data Entity Dictionary usage across the disciplines. To this end, NOST encourages you to make your interest in such a group known by contacting one of the authors at your earliest convenience.

Workshop on Digital Archive Directions Planned for June 1998

In the previous issue we also discussed Reference Model for Open Archive Information System (OAIS). Development of the the Reference Model will soon be completed and plans for a Digital Archive Directions (DADs) Workshop to prioritize future archiving standards activities are underway. To provide some context for this workshop, a brief history is given.

In 1995, the ISO requested the Consultative Committee for Space Data Standards (CCSDS) to develop standards for data archiving as a natural extension of its work in standardizing data interchange structures.

The team assessing this effort, in attempting to identify the general requirements for data archiving, quickly found several critical factors which needed to be addressed. These included the large number of organizations working in many areas related to data archiving, a dynamic environment of both the rapidly evolving technology involved and the growing volume of various types of data needing to be archived , and no generally accepted understanding of just what constituted a long term data archive. The team decided early that some type of consensus reference model was needed to provide focus for this truly global effort.

To initiate this effort, an international symposium was held in the United States in October 1995. This event was attended by about 60 people from over 30 organizations representing commercial, governmental, and academic areas; about 20 papers were presented followed by a day of working group discussions. The highly successful first meeting reached agreement that

  1. the lack of common terminology was severely impacting inter-archive communication and
  2. development of a high level reference model for a generic OAIS would be a first-priority effort.
This model would provide a framework for understanding significant relationships among the entities of an archival environment and for the development of consistent standards or specifications supporting that environment.

In the ensuing period, a number of international OAIS workshops have been held as well as several national OAIS workshops. France, Britain, and United States are examples of the latter activity. These workshops have individually and collectively progressed the OAIS Reference Model (RM) to a point where it is nearly ready for wide review. Plans are for this Reference Model to be submitted to ISO TC20/SC-13 as a Draft International Standard (DIS) during 1998.

Perhaps the most basic concept of the OAIS Reference Model is encompassed in the Archival Information Package (AIP) which contains the primary data to be stored, the descriptions of that data and the accompanying Preservation Description Information. (The Submission Information Package and the Dissemination Information Package are also defined and they can be viewed as modifications to the Archive Information Package as necessitated by the purposes of submission and dissemination.) The model also identifies six functional areas within an OAIS: Ingest, Storage, Data Management, Administration, Access, and Dissemination. The document defines and describes each area in detail and includes illustrative scenarios.

Current plans are to hold a second US/International Archiving Workshop in June 1998. The purpose of this workshop is

  1. to review and explain the OAIS Reference Model,
  2. to determine what standards a broad spectrum of digital archive supporters believe is currently needed,
  3. to assess the level of support for working such standards, and
  4. to help civil agencies and commercial organizations to make decisions as what standards developments they will directly support.

This second workshop, DADs Workshop, will be held from June 22 through June 26, 1998 at the National Archives in College Park, Maryland. Attendance may need to be limited to those who submit a position paper on why a particular standard is needed. These papers need not be more than one page in length.

Should you be interested in participating, for further information, please contact one of the authors.

Mr. John Garrett
Goddard Space Flight Center
Code 633
Greenbelt, MD 20771
United States
Telephone: +1.301.286.3575
FAX: +1.301.286.1771
Mr. Donald Sawyer
Goddard Space Flight Center
Code 633
Greenbelt, MD 20771
United States
Telephone: +1.301.286.2748
FAX: +1.301.286.1771
Mr. Robert Stephens
2211 Reedie Drive
Wheaton, MD 20902
United States
Telephone: +1.301.949.0965

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Miranda Beall,, (301) 286-0162
Raytheon STX, Code 633, NASA Goddard Space Flight Center
Greenbelt, MD 20771, U.S.A.

Erin D. Gardner,, (301) 286-0163
Raytheon STX, Code 633, NASA Goddard Space Flight Center
Greenbelt, MD 20771, U.S.A.

NASA home page GSFC home page GSFC organizational page

Authors:John Garrett, Donald Sawyer, and Robert Stephens
Curators: Erin Gardner and Miranda Beall
Responsible Official: Dr. Joseph H. King, Code 633
Last Revised: 4 MAR 1998 [JGG]