The DICOM File Service offers the ability to create and access one or more files in a File-set. A File-set is a collection of files that share a common naming space within which File IDs (see Section 8.2) are unique. No semantics is attached to the order of Files within a File-set.
Notes: 1. The DICOM File Service does not require that Files within a File-set be simultaneously accessible (e.g., sequentially accessed media such as tapes are supported).
2. The DICOM File Service does not explicitly include the notion of distributing a File-set or a File across multiple "volumes/physical medium". However the transparent support by the Media Format Layer of such a feature is not precluded.
A File ID naming space (corresponding to a File-set) shall be associated with an appropriate feature of a Media Format defined structure. This mapping shall be specified in PS 3.12 for each Media Format specification (this is integral to the specification of the relationship between any specific Media Format services and the DICOM File Services defined in this PS 3.10).
Note: An example of such a relationship is to map the File ID naming space to a volume in a personal computer Media Format or a partition in a workstation File System on a removable medium. Another example is to map the File ID naming space to a directory and its tree of subdirectories. In this case it could offer the possibility of supporting multiple File-sets (one per directory) on the same physical medium. Each File-set would have its own DICOMDIR File. To ensure interoperability, PS 3.12 shall specify these specific mapping rules between the directories and the File ID naming space of a File-set (including the rules to unambiguously locate the DICOMDIR File).
A single File with the File ID DICOMDIR shall be included in each File-set.
Each File-set shall be uniquely identified by a File-set UID which shall be registered according to the UID registration rules specified in PS 3.5 of the DICOM Standard. When Files are added or removed from a File-set, the File-set UID shall not change.
A File-set may also be identified by a File-set ID, which provides a simple (but possibly not globally unique) human readable reference. A File-set ID is string of zero (0) to sixteen (16) characters from the subset of the G0 repertoire of ISO 8859 (see Section 8.5). A File-set ID may be associated or mapped to an appropriate identifier at the Media Format Layer.
Notes: 1. Continuing with the personal computer Media Format example used first in the previous note, a File-set ID may be defined to be identical to a volume label.
2. Non-DICOM Files (Files with a content not formatted according to the requirements of this Part of the DICOM Standard) may be present in a File-set. Such files should not contain the DICOM File Meta Information specified in Table 7.1-1 and may not be referenced by the DICOM Media Storage Directory (See Section 8.6).
A File-set Descriptor File (a "readme" file) may also be attached to a File-set. See PS 3.3 for a detailed specification of the Basic Directory IOD.