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Related Materiel Positive Inventory Control

Archive Physical Organization
2B.1 PDS Data Storage and Access
Storage and accessibility of data within PDS must meet system requirements, which are
addressed elsewhere3
. Except for file and directory naming (Section 6C) and the restrictions
immediately below, no standards are set within this document for the organization of the
physical archive (i.e., there are no requirements for how the data are stored within or accessed
from a physical repository or data storage).
2B.1.1 Objects and Files
PDS requires that each digital object be physically distinct and contiguous in a single file;
objects may not overlap. For example, a color image may be stored as three separate
Array_2D_Image (RGB) objects with each of the R, G, and B components being stored
separately. The lines or samples of the three components may not be interleaved in this case.
However, it is permissible to define such an image as a single Array_3D_Image object with
interleaved lines or samples.
Although a single file may contain multiple digital objects, no digital object may extend beyond
a single file. For example, the R, G, and B image components above may be stored (in that
order) in a single file. Having any component (e.g., R, G or B) start in one file and continue into
a second file is not allowed.
A label and all of its associated digital objects must be stored in the same directory unless the
directory_path_name attribute is available, in which case directory_path_name may be used to
indicate a subdirectory relative to the directory containing the label.
2B.2 Data Transfer
The parties involved in a data transfer to, from, or within PDS are free to adopt any procedure
that is mutually acceptable. In lieu of such an ad hoc agreement, the following will be used.
2B.2.1 Transfer Media
The parties involved in a data transfer must agree on the physical media and interfaces to be used
(magnetic tape, CD, DVD, magnetic disk, electronic, etc.). PDS defers to industry standards for
the media selected.
2B.2.2 Directory Structure
Data will be transferred using a directory structure that parallels the logical organization of a
corresponding bundle (Section 2A). Note that the directory structure does not itself have to meet
the requirements for logical bundles or collections. Many transfers will contain only a portion of
a bundle or collection.