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A STANDARD METHOD FOR CREATING SELF-DEFINING 
DATA STRUCTURES FOR INFORMATION ARCHIVE AND TRANSFER 
John A. Johnson 
Jet Propulsion Laboratory 
California Institute of Technology 
Pasadena, California 
ABSTRACT 
A primary focus of Information Systems activities is to provide the techniques and tools to 
enable scientists and other data users to locate, acquire, and utilize data in the continuing 
search for understanding. This requires the interfacing of a myriad of data centers and data 
archives providing access to their data sets, unique application processes, and supporting 
tools and services. 
The growth in scientific understanding is based upon our ability to archive and access 
acquired information. At present, the data user community is diverse, disassociated, and 
discipline focused, and utilizes heterogenous processors. This places stringent data 
documentation requirements upon the users to facilitate a common understanding of the 
transferred data. Information transfer must include not only the application data bits, but 
also the ancillary data needed for meaningful analysis. In addition all data must be uniquely 
identified, and its syntax and semantics rigorously defined and included. 
This work is being done under the auspices of the Consultative Committee for Space Data 
Systems (CCSDS), an international organization of nine member space agencies. 
BACKGROUND: The Problem 
A typical single project data system of the recent past is depicted in figure 1. One or more 
instruments generate data streams which are captured and logged. The data are processed, 
loaded onto tapes, one copy of which is kept by the project, the other sent to the 
investigator. Ancillary data (engineering, monitor, navigation, etc.) are created and written 
to tape by other processors and sent to the investigator. Descriptions of these data types 
are documented in interface specifications. 
When the project ends, the archived copies of data and the documentation are warehoused; 
subsequent access to which, in most cases, is difficult. Identification of data (type, time, 
location, etc.) is quite often limited to a label on the tape reel and perhaps a few bytes at 
the beginning of each tape file. If data catalogs were produced, they are either warehoused