P.2 File System
Prev | P 120 mm DVD Medium (Normative) | Next

## P.2 File System

The reader shall be able to read a logical format conforming to UDF and ISO 9660 file systems, as defined below.

The creator shall be able to create a logical format conforming to UDF or ISO 9660 file systems or both, as defined below.

No requirements are defined for an updater.

### Note

The intent of these requirements is to insist that a reader be able to read media created by any creator, but not to require that media created by a particular creator can necessarily be updated by a different updater.

### P.2.1 UDF File System

The reader shall be able to read a logical format conforming to UDF 1.02 or 1.5 or 2.0 or 2.01, as required by the UDF 2.01 standard.

The creator shall be able to create a logical format conforming to any one of UDF 1.02 or 1.5 or 2.0 or 2.01.

Options or extensions defined in UDF are required or restricted as specified in the following sub-sections, and in the media specific sub-sections.

### Note

Though the names of the files within the DICOM File set are restricted by PS3.10, other files on the media may have longer file names.

#### P.2.1.1 Interchange Levels

For the UDF Primary Volume Descriptor, both the Interchange Level and Maximum Interchange Level shall always be set to 2.

### Note

1. This means that the volume is not and will never be, part of a multi-volume set.

2. The Interchange Level and Maximum Interchange Level in the File Set Descriptor are defined by UDF to always be 3. This is despite the fact that restrictions specified for the DICOM File-set may be very similar to lower Interchange Levels specified in ECMA 167.

#### P.2.1.2 Virtual Partition Map and Allocation Tables

Creators and updaters may or may not write UDF Virtual Partition Maps and Virtual Allocation Tables depending on the appropriate choice for physical media.

All readers are required to support UDF Virtual Partition Maps and Virtual Allocation Tables.

#### P.2.1.3 Sparable Partition Maps and Sparing Tables

Creators and updaters may or may not write UDF Sparable Partition Maps and Sparing Tables depending on the appropriate choice for physical media, since defect management may or may not be performed in the drive.

All readers are required to support UDF Sparable Partition Maps and Sparing Tables.

#### P.2.1.4 System Dependent Requirements

The reader shall not depend on any system dependent requirements as specified in UDF to be able to read the DICOM File-set, and shall not behave differently if they are present. Any unrecognized system dependent requirements shall be gracefully ignored.

Creators and updaters writing to a version of UDF that supports Named Streams shall use the default stream to write each file within the DICOM File-set.

### Note

1. For example, a particular form of file permissions, particular extended attributes or particular named streams may not be required or affect application behavior.

2. This does not mean that Extended Attributes or Named Streams may not be present and associated with files within the DICOM File-set.

#### P.2.1.5 Permissions and File Characteristics

Creators and updaters shall always create permissions for files within the DICOM File Set such that all users may read, write and delete all files, and all users may access and delete all directories on all systems.

### Note

1. These requirements are equivalent to setting a Unix permission of 644 for files and 755 for directories.

2. The intent of these requirements is that for DICOM interchange media, implementation specific access control is not used or required.

The UDF File Identifier Descriptor for files within the DICOM File Set shall not specify a File Characteristic of "hidden."

#### P.2.1.6 File Types

The UDF File Types within the DICOM File Set shall only be files (that is a File Type of 0, meaning unspecified interpretation) or symbolic links to files (that is a File Type of 12).

### P.2.2 ISO 9660 File System

The reader shall be able to read a logical format conforming to ISO 9660 Level 1, 2 and 3, with or without Rockridge or Joliet Extensions, which may or may not be present.

The creator shall be able to create a logical format conforming to ISO 9660 Level 1, 2 or 3, and may or may not add Rockridge or Joliet Extensions.

### Note

Though the files within the DICOM File set are restricted to names that conform to a subset of ISO 9660 Level 1, other files on the media may have longer file names. Unlike the Annex of this part specifying CD-R media, strict Level 1 conformance of the file system is not required, since this has proven difficult to constrain in practice.

#### P.2.2.1 Extended Attributes, Permissions and File Characteristics

File modification data, file owner identification, and permissions are part of the ISO 9660 - Extended Attribute Record. Support of the Extended Attribute Record is not required.

If Extended Attribute Records are present, all files within the DICOM File Set shall have permissions such that all users may read all files, and all users may access all directories on all systems.

### Note

The intent of these requirements is that for DICOM interchange media, implementation specific access control is not used or required.

Prev | Up | Next
P 120 mm DVD Medium (Normative) | Home | P.3 Media Formats