Consider a call such as: 
Select XXX from yyy in format zzz. 
FILE REQUEST 
yyy 
DATA ELEMENT REQ- 
XXX 
REFORMAT REQUEST 
zzz 
DATA ELEMENT SENT 
TO REQUESTER 
MODEL FOR DATA ELEMENT RETRIEVAL AND CONVERSION 
TSDN Status 
The TSDN is being developed at the Jet Propulsion Laboratory, Californua 
Institute of Technology, under the auspicies of the Consultative Committee 
on Space Data Systems, under a contract with the National Aeronautics and 
Space Administration. It has been accepted by ANSI as a new work item; it 
is hoped that it will be imminently ready for public review. Further 
information is available from the authors, and comments will be 
appreciated.