Figure 4: Data Object/DDU Relationship
ADI=CCSD0001) contains three TLVOs. The first (class C, ADI=CCSD0004) contains
the name of the unit; that is, the statement ADI=INPE1234 is used by the referencing I
class data object (class I, ADI=INPE1234). The second (class D, ADI=NJPLL006)
contains Fortran source to read the content of the I class data object. The third (class E,
ADI=ESSD8111) contains the DED giving semantic information about the data.
The data description information must be in place on the data user’s processor before the
data that needs it are processed. This means that the data description information, if
packaged with the data product, must precede the data object. It can also be transmitted
separately ahead of time. An example of an automated implementation is as follows: The
data description information upon arrival is logged into a library or database system, keyed
on the ADI extracted from the Class C TLVO. When a data object with that ADI is
received, the corresponding data description information is retrieved from the library, using
this ADI as a key. The description metadata may then be used to extract the data elements.
REFERENCES
1. J.A.Johnson, ed., Standard Formatted Data Units - Structure and Construction
Rules. CCSDS 620.0-R-l, November 1989.
2. J.AJohnson, ed., Standard Formatted Data Units - Product Aggregation Aspects.
CCSDS 620.0-G-l, November 1989.
The research described in this paper was carried out by the Jet Propulsion
Laboratory, California Institute of Technology, under a contract with the
National Aeronautics and Space Administration.
