Chapter 8.

Directory Types and Naming 8-1

Chapter 8. Directory Types and Naming

The Directory Naming standard defines the conventions for naming directories on a data volume.
This chapter lists the standard directories established by PDS, plus the rules for forming
subdirectory names and abbreviations.

8.1 Standard Directory Names

When any of the following directories are included on an archive product, the following standard
directory naming conventions are used.

Directory Contents
CATALOG PDS catalog files

DOCUMENT Documentation, supplementary and ancillary information to assist in

understanding and using the data products

EXTRAS “Value added” elements included by the data preparer, but outside the scope
of the PDS archive requirements

GAZETTER Tables of information about the geological features of a target

INDEX Indices to assist in locating data of interest

LABEL “Include” files which describe specific aspects of the data format and
organization

SOFTWARE Utilities, application programs, or subprograms used to access or process the

data

The following standard directory names are recommended for use on archive volumes. Note that
these directory names are reserved for the uses described below. That is, if they appear on an
archive volume, they must contain the indicated information:

CALIB Calibration files used in the original processing of the data, or needed to use
the data

GEOMETRY Files describing the observational geometry (e.g., SEDRs, SPICE kernels)

BROWSE Reduced resolution versions of data products

DATA Contains one or more subdirectories of data products. The DATA

subdirectory is used to unclutter the root directory of a volume by providing a
single entry point to multiple data subdirectories.
8-2 Chapter 8. Directory Types and Naming

Note that some data sets may not contain all the components above and, as a result, do not need
all of the directories listed. For example, many image data sets do not include geometry files and
so do not need a GEOMETRY directory. See the Volume Organization and Naming chapter of
this document for a list of required and optional subdirectories on any specific volume.

8.2 Formation of Directory Names

1. A directory name must consist of only uppercase alphanumeric characters and the
underscore character (i.e., A-Z, 0-9, or “_”). No lowercase letters (i.e., a-z) or special
characters (e.g., “#”, “&”, “*”) are allowed.
2. Directory names must comply with the ISO 9660 Level 2 standard and not exceed 31
characters in length. Users are encouraged to keep directory names as brief as practical
in the interests of providing succinct file paths and easy to read directory listings.
3. The first letter of a directory name must be an alphabetic character, unless the directory
name represents a year (e.g., 1984).
4. If numeric characters are used as part of the name (e.g., DIR1, DIR2, DIR3) the numeric
part should be padded with leading zeros up to the maximum size of the numeric
(DIR0001, DIR0002, DIR3267).
5. Directories which contain a range of similarly named files must be assigned directory
names using the portion of the filename which encompasses all the files in the directory,
with “X’s” used to indicate the range of values of actual filenames in the directory.
For example, the PDS Uranus Imaging CD-ROM disk contains image files that have
filenames that correspond to SPACECRAFT_CLOCK_START_COUNT values. The
directory that contains the image files ranging from C2674702.IMG through
C2674959.IMG has the directory name C2674XXX.

6. Directory names must use full length terms whenever possible (e.g., SATURN,
MAGELLAN, CRUISE, NORTH, DATA, SOFTWARE). Otherwise, directory names
must be constructed from abbreviations of full-length names using the underscore
character to separate abbreviated terms, if possible. The meaning of the directory name
should be clear from the abbreviation and from the directory structure.
Chapter 8. Directory Types and Naming 8-3

For example, the following directory structure can be found on the Voyager 2 Images of
Uranus CD-ROM Volume 1:

ROOT ARIEL
DOCUMENT
INDEX
OBERON
TITANIA
UMBRIEL
UNKNOWN
URANUS C2674XXX
C2675XXX
…
C2687XXX
U_RINGS C2674XXX
…

In this case, it is clear from the context that the directory U_RINGS is the abbreviated
form of URANUS_RINGS.

7. High level directories that deal with data sets covering a range of planetary science
disciplines or targets shall adhere to the following hierarchy:

A Planetary science directory: PLANET

Planetary body subdirectories: MERCURY, MOON, MARS, VENUS, COMET
Discipline subdirectories: ATMOS, IONOSPHE, MAGNETOS, RING,
SURFACE, and SATELLIT
(Use satellite name if numerous files exist)

8. The recommended SOFTWARE subdirectory naming convention is described in the

Volume Organization and Naming chapter of this document. Either a platform-based
model or an application-based model can be used in defining software subdirectories. In
a platform-based model, the hardware platform, operating system and environment must
be explicitly stated. If there is more than one operating system/environment supported
they are addressed as subdirectories under the hardware directories. When there is only
one, the subdirectory may be promoted to the hardware directory.

For example, if software for the PC for both DOS and Windows were present on the
volume, the directories SOFTWARE/PC/DOS and SOFTWARE/PC/WIN would exist. If
only DOS software were present, the directory would be SOFTWARE/PCDOS.
8-4 Chapter 8. Directory Types and Naming

8.3 Path Formation Standard

The PDS standard for path names is based on Level 2 of the ISO 9660 international standard. A
pathname may consist of up to eight directory levels. Each directory name is limited to 31
characters; the forward-slash character (“/”) is used as the separator in path names. Path names
typically appear on PDS volumes as data in index tables for locating specific files on an archive
volume. They may also appear as values in a limited number of keywords (e.g.,
FILE_SPECIFICATION_NAME, PATH_NAME, and LOGICAL_VOLUME_PATH_NAME).

The following are examples of valid values for the keywords listed above:

TG15NXXX/TG15N1XX/TG15N12X identifies the location of the directory TG15N12X

at the third level below the top level of an archive
volume.

DOCUMENT identifies a DOCUMENT directory within the root

directory.

Note: The leading slash is omitted because these are relative paths. The trailing slash is
included so that concatenation of PATH_NAME and FILE_NAME will yield the full file
specification. See the File Specification and Naming chapter of this document for more
information.

Previous PDS standards allowed the use of the DEC VMS syntax for path names. While PDS
support for this format continues to exist, it is recommended that all future volumes use the
UNIX syntax instead.

8.4 Tape Volumes

When magnetic tape is the archive medium, a disk directory structure cannot be used because the
medium does not support multi-level directories. In this case, files must be stored sequentially.

A directory structure for the volume must be designed in any case, so that when the data are
transferred to a medium that supports hierarchical file management they can be placed into an
appropriate directory structure. A DIRECTORY object must be included with each tape volume
within the VOLUME object. This object is then used to describe how the sequential files should
be loaded into a hierarchical structure.

8.5 Exceptions to These Standards

In certain cases, the archive medium used to store the data, the hardware used to produce the data
set, or the software operating on the data may impose restrictions on directory names and
organization. In these cases, consult a PDS data engineer for guidance in designing the archive
volume structure.
Chapter 8. Directory Types and Naming 8-5

directories
path names, 8-4
reserved names, 8-1
standard directories, 8-1
DIRECTORY, 8-4
directory names
, 8-2
syntax, 8-2
directory naming, 8-1
directory paths
and ISO 9660, 8-4
syntax, 8-4
directory structure
example, 8-3
on sequential media, 8-4
tape volumes, 8-4
VOLUME, 8-4