STANDARDS CHANGE REQUEST - DVD Case Standards
=============================================

Purpose: Change the directory and file naming rules so that lower case names
are used for DVD archive volumes. Upper case names will continue to be used
for CD (CD-ROM or CD-R) archive volumes.

NOTE: Changes to the definition of a "PDS Volume," driven by electronic data
delivery, online distribution, and the creation of "archive packages" for the
NSSDC, are not covered in this SCR.

Date: 2004-11-26, revision 2.1

Working Group: J. Wilf (lead), C. Isbell, C. Hall-Atkinson, M. McAuley, and
L. Huber


Background
==========
When Chapter 19 of the PDS Standards, "Volume Organization and Naming," was
written, it was intended specifically for archive volumes written to compact
optical disc (CD) media. It therefore followed the ISO-9660 standard, which 
specifies the file and volume structure for CD media  and requires UPPER CASE
directory and file names.

As PDS data volume grew, it became necessary to move to the higher-capacity
DVD media. The Data Distribution Laboratory (DDL), which had helped develop
the PDS standards for CD media volumes, made the following recommendations 
for DVD. These were based on extensive media testing, with the purpose of
ensuring the most uniform ability to read and write DVD media across all
computer platforms:

1) Write DVD media using the UDF-ISO bridge format, where UDF (Universal Disk
Format) is a filesystem standard chosen for DVD and higher-capacity media, and
where the UDF-ISO bridge format creates both an ISO-9660 and UDF partition on
the DVD.

2) Convert all directory and file names to lower case before writing the DVD.
This leads to a lower-case UDF partition and an upper-case ISO-9660 partition,
since the DVD-writing software automatically does lower-to-UPPER case 
conversion for the ISO-9660 partition. Case is preserved within the UDF
partition.

Although the UDF partition can accept either upper or lower-case names, there
were several reasons for choosing lower-case. DDL testing showed that the
lower-case UDF partition was read correctly across Windows, Solaris, Linux,
and Mac platforms, whereas an upper-case UDF partition was read incorrectly on
Windows as having an upper-case first character, followed by lower-case
subsequent characters. Also, user interface studies have shown that lower-case
directory and file names are far more readable. Finally, it should be noted
that lower-case directory and file names have also been recommended for use in
the online repositories from which archive data are distributed.


Current Urgency
===============
The MGS-Extended and NEAR missions have already delivered archive data on
DVD media, and the Cassini mission is planning to do so in the near future.

It is understood that fundamental changes are coming to the definition of
a "PDS Volume" -- changes driven by the electronic delivery of data, the
distribution of data from online repositories, and the creation of archive
packages for preservation by the NSSDC. However, in the short term, it is
important that the published PDS Standards reflect the current mission needs,
and so it is recommended that the DVD directory and file naming conventions
described here should be published in the upcoming version of the Standards, 
and that the larger design changes to the "PDS Volume" should be handled in a
separate SCR.


Recommendations
===============
Given the urgency described above, the PDS Project Engineer recommends
the following actions:

1. To Management Council: Approve the DVD CASE SCR as soon as possible.

2. To the PDS Standards Lead: Upon Management Council approval, publish
the changes in the next version of the PDS Standards Reference, as described
in the paragraphs below.


Changes to the Standards Reference 
==================================
The following changes to the PDS Standards Reference are required to
support this SCR:

1. Chapter 11, "Media Formats for Data Submission and Archive," will be
   updated, where needed, to reflect the latest DVD-writing recommendations,
   given in the white paper "Mars Odyssey Archive Options" by Chris Isbell
   and Cynthia Hall-Atkinson, June 2003. This will include the recommendation
   to use lower-case directory and file names.

2. Chapter 19, "Volume Organization and Naming," will be updated with a 
   "NOTE on Upper vs. Lower Case Directory and File Naming." This note
   will appear in the introduction to the chapter and will make it clear
   that the upper-case names appearing in the chapter are to be used only
   on CD-ROM volumes, while lower-case names are to be used when writing
   DVD volumes. 

3. The standards for labels and index tables should be changed so that
   filenames are given in accordance with the media selected for archiving.
   That is, if it is intended to write a CD-ROM archive volume, then 
   upper case should be used. For all other situations, use lower case
   filenames in labels and index tables.

4. In general, the working group will need to go through the Standards
   Reference and find all references to file/directory naming and change
   accordingly. For example, as Lyle pointed out, there are changes in 
   Chapter 8 (e.g., Section 8.3) and Chapter 10.

[Note: Actual wording will be supplied when the concepts are agreed upon]


Changes to the Data Dictionary - None
==============================


Changes to the PDS Tool Suite - None
=============================


Impact Statement
================
The PDS Standards Reference will be modified as described above. There are
no other known impacts to the PDS System.


Open Issues
===========
As noted above, major changes will be made to the concept of a "PDS Volume,"
but these are beyond the scope of the current SCR.


[END OF SCR]