| First Indicator | Second Indicator |
|---|---|
| Undefined # - Undefined |
148/448/548 - Undefined # - Undefined 748 - Thesaurus 0 - Library of Congress Subject Headings 1 - LC subject headings for children's literature 2 - Medical Subject Headings 3 - National Agricultural Library subject authority file 4 - Source not specified 5 - Canadian Subject Headings 6 - Répertoire de vedettes-matière 7 - Source specified in subfield $2 |
| Subfield Codes | |
|---|---|
|
Main term portion
Tracing and linking subfields
|
Subject subdivision portion
|
Content designators identify the subelements occurring in chronological term headings constructed according to generally accepted thesaurus-building conventions (e.g., Faceted Application of Subject Terminology (FAST)). Chronological terms include dates that are used as the lead element of subject or added entry access fields in bibliographic records. A chronological term that is authorized for use only as a subject subdivision part of an extended subject heading is contained in a 182 (Chronological Subdivision) field.
Only generally-applicable content designators are described in full in this section. A small number of content designators with field-specific instructions are described in the Tracings and References-General Information section (for fields 448 and 548) and the 7XX Heading Linking Entries-General Information section (for field 748).
First Indicator - Undefined
Undefined and contains a blank (#).
Second Indicator
In fields 148, 448, and 548, the second indicator position is undefined and contains a blank (#). For field 748, the second indicator position contains one of the values described in the 7XX Heading Linking Entries-General Information section.
$a - Chronological term
Chronological term used as an entry element.
| 748 | #7$a1710-1714$2fast | ||||||||
| 748 | #7$a1500-1700$2fast | ||||||||
| 148 | ##$a1863 | ||||||||
$i - Relationship information [448/548/748]
Designation of a relationship of the entity in a 448, 548, or 748 field to the 1XX entity in the record or a textual reference instruction phrase. For fields 448 and 548 the phrase may be system-generated from the field tag or from the codes defined for subfield $w (Control subfield). Subfield $i is appropriate only in fields 448, 548, and 748. Guidelines for using subfield $i in fields 448 and 548 are provided in the Tracings and References-General Information section. Guidelines for using subfield $i in field 748 are provided in the 7XX Heading Linking Entries-General Information section.
$v - Form subdivision
Designates a specific kind or genre of material as defined by the thesaurus being used. Subfield $v is appropriate in the X48 fields only when a form subject subdivision is added to a main term to form an extended heading.
$w - Control subfield [448/548/748]
Codes in one or more character positions defined to control the display of information and specify relationships, restrictions, and status. Subfield $w is appropriate only in fields 448, 548, and 748. Character position definitions and guidelines for applying the codes defined for subfield $w in fields 448 and 548 are provided in the Tracings and References-General Information section. Character position definitions and guidelines for field 748 are provided in the 7XX Heading Linking Entries-General Information section.
| 748 | #7$a1710-1714$2fast$wna | ||||||||
$x - General subdivision
Subject subdivision that is not more appropriately contained in subfield $v (Form subdivision), subfield $y (Chronological subdivision), and subfield $z (Geographic subdivision). Subfield $x is appropriate in the X48 fields only when a general topical subject subdivision is added to a main term to form an extended heading.
$y - Chronological subdivision
Subject subdivision that represents a period of time. Subfield $y is appropriate in the X48 fields only when a chronological subject subdivision is added to the main term to form an extended heading.
$z - Geographic subdivision
Appropriate in the X48 fields only when a geographic subject subdivision is added to a main term to form an extended heading.
$0 - Authority record control number or standard number [548/748]
See description of this subfield in Appendix A: Control Subfields.
$1 - Real World Object URI [548/748]
See description of this subfield in Appendix A: Control Subfields.
$2 - Source of heading or term [748]
Code that identifies the source of a heading or term when the second indicator position contains value 7. Subfield $2 is appropriate only in field 748. Guidelines for applying subfield $2 are provided in the 7XX Heading Linking Entries-General Information section.
| 748 | #7$a1900-1999$2fast | ||||||||
| 748 | #7$a1800-1899$2fast | ||||||||
$4 - Relationship [448/548/748]
Code or URI that specifies the relationship from the entity described in the record to the entity referenced in the field. Guidelines for using subfield $4 in fields 448 and 548 are provided in the Tracings and References-General Information section. Guidelines for using subfield $4 in field 748 are provided in the 7XX Heading Linking Entries-General Information section.
$5 - Institution to which field applies [448/548/748]
See description of this subfield in Appendix A: Control Subfields.
$6 - Linkage
See description of this subfield in Appendix A: Control Subfields.
$8 - Field link and sequence number
See description of this subfield in Appendix A: Control Subfields.
Punctuation - Punctuation of the subelements of a heading is generally dictated by subject heading system/thesaurus rules. These input conventions clarify MARC punctuation practices. An X48 field does not end with a mark of punctuation unless the field ends with an abbreviation, an initialism, or data that ends with a mark of punctuation.
Spacing - No spaces are used in initialisms, acronyms, or abbreviations. One space is used between preceding and succeeding initials if an abbreviation consists of more than a single letter. A data element that contains an open-ended date ends with one space when it is followed by a subject subdivision.
Display Constant
| - | [dash associated with the content of subfield $v, $x, $y, and $z] |
Dash (-) that precedes a subject subdivision in an extended subject heading is not carried in the MARC record. It may be system generated as a display constant associated with the content of subfield $v, $x, $y, and $z.
Subfield $4 was renamed and redescribed to allow for the recording of relationship URIs in addition to MARC and non-MARC codes.