F.3 Basic Directory IOD
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## F.3 Basic Directory IOD

This IOD is based on the Directory Information organization introduced in Section F.2. The model for this Basic Directory IOD is described Section F.2.1 by the Entity/Relationship model in Figure F.2-1. The rules specified in Section F.2.1 apply to this Information Object Definition.

### F.3.1 Module Table

The Basic Directory IOD includes the Modules specified by Table F.3-1.

Table F.3-1. Basic Directory IOD Modules

Module | Reference | Usage | Module Description
--- | --- | --- | ---
File-set Identification | F.3.2.1 | M | File-set identification information
Directory Information | F.3.2.2 | U | Directory Information followed by a Sequence of Directory Records. ### Note The Directory Information Module is optional. This Directory Information Module should be present in all but primitive environments where a directory is not needed. In this case, only the File-set Identification Information is present.

### F.3.2 Modules of the Basic Directory Information Object

Attributes of the Basic Directory IOD are defined with a Type designation that indicates if a specific Attribute is required for all Media Storage Operations (see Chapter 5).

#### F.3.2.1 File-set Identification Module

Table F.3-2. File-Set Identification Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
File-set ID | (0004,1130) | 2 | User or implementation specific Identifier (up to 16 characters). For definition, see PS3.10. The File-set ID is intended to be a short human readable label to easily (but not necessarily uniquely) identify a specific File-set to facilitate operator manipulation of the physical media on which the File-set is stored. Assignment of Value and semantics are environment specific.
File-set Descriptor File ID | (0004,1141) | 3 | ID of a File (in the same File-set) used for user comments related to the File-set (e.g., a README file). The Specific Character set used may be specified in the Specific Character Set of the File-set Descriptor File (0004,1142). ### Note This File is not DICOM formatted (no Preamble, nor DICM Prefix and Meta Information).
Specific Character Set of File-set Descriptor File | (0004,1142) | 1C | Character set used in the File-set Descriptor File with a File ID as specified in File-set Descriptor File ID (0004,1141). Required to specify the expanded or replacement character set. If absent, only the Basic Graphic set is used. See Section C.12.1.1.2 for Defined Terms.

### Note

Every File-set is assigned a File-set UID when created. The File-set UID need not be duplicated as a Type 1 Attribute of the File-set Identification Module. It is conveyed as the SOP Instance UID of the Basic Directory IOD. It is included in the DICOMDIR File Meta Information (see PS3.10)

#### F.3.2.2 Directory Information Module

This Module contains a sequence of Directory Records forming one or more Directory Entities. This Module defines at least one Directory Entity, the Root Directory Entity (which may be empty). Each Directory Record is composed of Directory Elements (marked by a ">"). They include:

1. an offset pointer to another Directory Record of the Same Directory Entity

2. an offset pointer to a lower level Directory Entity

3. a Referenced File pointed to by the Directory Record

4. a set of keys representative of the information contained in the Referenced File

Table F.3-3. Directory Information Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Offset of the First Directory Record of the Root Directory Entity | (0004,1200) | 1 | Offset of the first byte (of the Item Data Element) of the first Directory Record of the Root Directory Entity. This Offset is a number of bytes starting with the first byte of the File Meta Information. When the Root Directory Entity contains no Directory Record, this offset shall be set to 00000000H. ### Note This offset includes the File Preamble and the DICM Prefix.
Offset of the Last Directory Record of the Root Directory Entity | (0004,1202) | 1 | Offset of the first byte (of the Item Data Element) of the last Directory Record of the Root Directory Entity. This Offset is a number of bytes starting with the first byte of the File Meta Information. When the Root Directory Entity contains no Directory Record, this offset shall be set to 00000000H. ### Note This offset includes the File Preamble and the DICM Prefix.
File-set Consistency Flag | (0004,1212) | 1 | Enumerated Values: 0000H no known inconsistencies The value FFFFH shall never be sent. ### Note Formerly, this Attribute was intended to signal that the directory was in an inconsistent state with a value of FFFFH. This usage has been retired. See PS3.3-2008.
Directory Record Sequence | (0004,1220) | 2 | Sequence of zero or more Items where each Item contains a Directory Record by including the Directory Elements from (0004,1400) to (0004,1511) and Record selection Keys as defined below (marked with a >). A zero length Value indicates that no Directory Records are contained in the Root Directory Entity.
>Offset of the Next Directory Record | (0004,1400) | 1 | Offset of the first byte (of the Item Data Element) of the next Directory Record of the same Directory Entity. This Offset is an unsigned integer representing a number of bytes starting with the first byte of the File Meta-information. A zero offset shall be used to mean that there is no other Directory Record in this Directory Entity. This Offset may be used to keep an inactive Record (0004,1410) chained with the next Directory Record of the same Directory Entity. ### Note This offset includes the File Preamble and the DICM Prefix.
>Record In-use Flag | (0004,1410) | 1 | Enumerated Values: FFFFH record is in use. The value 0000H shall never be sent. ### Note Formerly, this Attribute was intended to facilitate the deletion of files, with a value 0000H signally an inactive record. This usage has been retired. See PS3.3-2008. Other Values are reserved and shall not be set by File-set Creators, but if present shall be interpreted as FFFFH by File-set Readers or Updaters.
>Offset of Referenced Lower-Level Directory Entity | (0004,1420) | 1 | Offset of the first byte (of the Item Data Element) of the first Directory Record of the Referenced Lower Level Directory Entity. This Offset is a number of bytes starting with the first byte of the File Meta Information. When no lower-level Directory Entity (containing at least one Directory Record) is referenced, this Attribute shall have a Value of 00000000H. ### Note This offset includes the File Preamble and the DICM Prefix.
>Directory Record Type | (0004,1430) | 1 | Defines a specialized type of Directory Record by reference to its position in the Media Storage Directory Information Model (see Section F.4). Enumerated Values: PATIENT STUDY SERIES IMAGE RT DOSE RT STRUCTURE SET RT PLAN RT TREAT RECORD PRESENTATION WAVEFORM SR DOCUMENT KEY OBJECT DOC SPECTROSCOPY RAW DATA REGISTRATION FIDUCIAL HANGING PROTOCOL ENCAP DOC HL7 STRUC DOC VALUE MAP STEREOMETRIC PALETTE IMPLANT IMPLANT GROUP IMPLANT ASSY MEASUREMENT SURFACE SURFACE SCAN PRIVATE Privately defined record hierarchy position. Type shall be defined by Private Record UID (0004,1432). ### Note Enumerated Values PRINT QUEUE, FILM SESSION, FILM BOX, and IMAGE BOX were previously defined in DICOM for this Attribute. They are now retired. See PS3.3-1998. Enumerated Values OVERLAY, MODALITY LUT, VOI LUT, CURVE, TOPIC, VISIT, RESULTS, INTERPRETATION, STUDY COMPONENT and STORED PRINT were previously defined in DICOM for this Attribute. They are now retired. See PS3.3-2004. Enumerated Value MRDR was previously defined in DICOM for this Attribute, to allow indirect reference to a File by multiple Directory Records. It is now retired. FSUs and FSRs are unlikely to be capable of supporting this mechanism. See PS3.3-2004.
>Private Record UID | (0004,1432) | 1C | Required if the Directory Record Type (0004,1430) is of Value PRIVATE. This UID is used to define a non-standard type of Directory Record by reference to its position in a private extension to the Basic Directory IOD Information Model (see Section F.5). This UID shall be registered according to the procedures defined in PS3.5. Its meaning may or may not be specified in a Conformance Statement.
>Referenced File ID | (0004,1500) | 1C | A Multiple Value (see PS3.5) that represents the ordered components of the File ID containing a "referenced object" or Referenced SOP Instance. A maximum of 8 components, each from 1 to 8 characters shall be used (see Section 8.2). ### Note The Referenced File ID provides the means to "locate" the File through the DICOM File Service provided by the Media Format Layer. All referenced Files shall be with the File-set to which the Directory belongs. Any File within the File-set (to which the Directory belongs) shall be referenced by at most one Directory Record. When the Directory Record does not reference any SOP Instance this attribute shall not be present.
>Referenced SOP Class UID in File | (0004,1510) | 1C | Unique ID for the SOP Class of the Instance stored in the referenced File. Required if the Directory Record references a SOP Instance.
>Referenced SOP Instance UID in File | (0004,1511) | 1C | Unique Identifier for the SOP Instance stored in the referenced file. Required if the Directory Record references a SOP Instance.
>Referenced Transfer Syntax UID in File | (0004,1512) | 1C | Unique Identifier for the Transfer Syntax used to encode the Instance stored in the referenced file. Required if the Directory Record references a SOP Instance.
>Referenced Related General SOP Class UID in File | (0004,151A) | 1C | Unique ID for the Related General SOP Class(es) related to the SOP Class of the Instance stored in the referenced file. Required if the Directory Record references a SOP Instance that encodes the Related General SOP Class UID (0008,001A). ### Note This may be useful to an FSR that does not support the SOP Class of the referenced Instance, but does support one of the Related General SOP Classes.
>Record Selection Keys | See F.5 | See F.5 | A number of DICOM Data Elements that contain specific keys defined for each type of Directory Record (0004,1430) defined in Section F.5.

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