[Smwg] Updated XFDU in TGFT Tech Note on CWE

[John Pietras]

CSSMWG colleagues ---
In the process of preparing the presentation of the overview of the XFDU in TGFT Tech Note for last week's meeting, I discovered a few errors in the Tech Note. I have made a minor update to correct those errors, which are identified in the DOCUMENTO CONROL section at the beginning of the document.

During the discussion at the meeting itself, a point was raised regarding whether the following paragraph in section 2.3 was in error:
"Similar to payload data, the CCSDS-standard XFDU allows metadata to be carried in the XFDU Package in either of two ways: embedded in the XFDU Manifest itself, or as separate files that are contained in the ZIP/TAR XFDU Package and referenced by the XFDU Manifest. However, for TGFT only the separate-metadata-file(s)-within-the-XFDU-Package approach is supported."

During the discussion I agreed that the paragraph was in error. However, upon further review following the meeting, I have determined that paragraph is actually correct after all. The statement in contention was the first sentence, which states that that metadata be carried either embedded in the XFDU Manifest or as a separate file within the same zipped/tarred CFDU Package, which is NOT the case for TGFT XFDUs. However, this first sentence applies to the original CCSDS XFDU Manifest, not the TGFT XFDU. It is the SECOND sentence that refers to the TGFT XFDU, and the restriction is properly stated there. In order to reduce the possibility for this confusion in the future, I have added emphasis so that the paragraph now reads:
"Similar to payload data, the original CCSDS-standard XFDU allows metadata to be carried in the XFDU Package in either of two ways: embedded in the XFDU Manifest itself, or as separate files that are contained in the ZIP/TAR XFDU Package and referenced by the XFDU Manifest. However, for TGFT only the separate-metadata-file(s)-within-the-XFDU-Package approach is supported.
Along with the Tech Note itself, I have also included four other files:

-          The original CCSDS XFDU schema

-          A trimmed-down version of the schema that supports only the features that are supported for TGFT

-          The  TfgtXfduExtensionParameters.xsd schema file, and

-          The XFDU Manifest XML file for the TDM example presented in Annex B of the Tech Note.

I have bundled these five files together into a zipped file which itself is an XFDU Package that conforms to the TGFT constraints. The file XFDU_in_TGFT_TechNote-v0x5.xfdu is the XFDU Manifest for the Package - change the ".xfdu" extension to ".xml" and it will validate as an XFDU Manifest and act as the "road map" for the other 5 files in the Package.

The XFDU Package has been uploaded to the new CSS-SM/CWE Private - Beta/Tech Note Development/XFDU in TGFT Tech Note folder at
https://cwe.ccsds.org/css/docs/CSS-SM/CWE%20Private%20-%20Beta/Tech%20Note%20Development/XFDU%20in%20TGFT%20Tech%20Note/XFDU_in_TGFT_TechNote-v0x5_Package-2017-137T16-46-00Z.zip

The name of the XFDU Package, XFDU_in_TGFT_TechNote-v0x5_Package-2017-137T16-46-00Z.zip, conforms to the naming conversion proposed by Colin in the TGFT White Book and modified in the Tech Note, where "XFDU_in_TGFT_TechNote-v0x5_Package" constitutes the service-specific part of the name and "2017-137T16-46-00Z" is the timestamp corresponding to the beginning of the transfer of file to the CWE in modified CCSDS ASCII Time Code B format (which substitutes dashes ("-") for colons (":") for universal support by file systems).

Best regards,
John
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