NAME: Definition of Subfield $v for Form Subdivision in the USMARC Formats
SOURCE: ALA/ALCTS Subject Analysis Committee
SUMMARY: This paper proposes a new subfield $v for form subdivisions in fields 6XX and 755 in the bibliographic format, 1XX, 4XX, and 5XX in the authority format, 75X in the classification format, and 6XX in the community information format and new fields 183, 483, 583, and 783 for subdivision headings in the authority format. It reviews the desirability for such a subfield and discusses technical issues involved in implementing such a change. It poses questions on retrospective conversion, issues of authority control and implementation options.
KEYWORDS: Subfield $v (Bibliographic/Authority/Classification/ Community Information); Form Subdivisions; Field 183 (Authority); Field 483 (Authority); Field 583 (Authority); Field 783 (Authority)
RELATED: DP79 (June 1994); DP74 (February 1994)
STATUS/COMMENTS:
12/2/94 - Forwarded to USMARC Advisory Group for discussion at the February 1995 MARBI meetings.
2/16/95 - Results of USMARC Advisory Group discussion - Approved as amended.
The description of subfield $k (Form subheading) needs to be changed so that there is not confusion with subfield $v. The field tag should be changed to 185, 485, 585, 785 in the authority format for Form subdivision. Examples need to be added for thesauri other than LCSH (MeSH, AAT). With the approval of this proposal, thesauri other than LCSH can begin to use subfield $v.
LC was encouraged to develop a plan for implementation for LCSH. Discussion indicated that to do so LC will need to consider the following issues:
1) look at the list of form subdivisions to determine which are dual functioning
2) global update at LC will need to be in place before any retrospective conversion
3) SAC will work with LC to plan possible implementation (which may be phased in over a period of time, coordinated with other parties)
4) LC will look at possible algorithms for conversion; discussion may be on USMARC list
5) Studies concerning possible OPAC displays need to be conducted. Vendors will need input on this; SAC is looking at display issues
6) LC needs to develop a plan for the use of field 655
2/16/95 - Results of final LC review - Agreed with the MARBI decisions.
PROPOSAL NO. 95-2: Definition of Subfield $v for Form Subdivision 1. BACKGROUND The Subject Subdivisions Conference was sponsored by the Library of Congress and held in May 1991 at Airlie House in Virginia to address subdivision practice in the Library of Congress subject headings system. Its purpose was to make the assignment of subject headings more efficient, to enhance and encourage cooperative cataloging efforts, and to improve subject access for online public access catalog users. Six recommendations resulted. Recommendation No. 4 suggested the addition of a separate subfield code for form subdivisions in subject heading fields of the USMARC bibliographic and authority formats. It stated: "4. The question of whether subdivisions should be coded specifically to improve online displays for end users should be considered by organizations such as the Network Development and MARC Standards Office at the Library of Congress, MARBI, the Subject Analysis Committee (SAC) of the American Library Association, and the utilities, among others. In particular, the Library of Congress should investigate implementing a separate subfield code for form subdivisions." As a follow-up to this recommendation, the ALA SAC Subcommittee on Nature and Use of Form Data formally submitted a request to the Network Development and MARC Standards Office to add a separate repeatable subfield code for form subdivisions, so that they can be distinguished from topical, geographic, and chronological subdivisions. Currently form subdivisions are put into subfield $x (General subdivision), although there are specific subfields for chronological ($y) and geographic ($z) subdivisions. Fields that would need this new subfield would be: 6XX (Subject Access fields), 755 (Added Entry--Physical Characteristics) in the bibliographic format (see Discussion Paper No. 82: Merging Field 755 with Field 655) considering the issue of making this field obsolete; 1XX (Headings), 4XX (See From Tracing fields), 5XX (See Also From Tracing fields) in the authority format; 75X (Index Term fields) in the classification format; and 6XX (Subject Access fields) in the community information format. If a new subfield code were defined for form subdivisions, then new fields would also be needed for form subdivision headings in the following areas: 18X (Heading), 48X (See From Tracing), 58X (See Also From Tracing), and 78X (Subdivision Linking Entry), as these fields exist for other types of subdivisions. Discussion Paper No. 79 was discussed at the June 1994 meetings of the USMARC Advisory Group. This paper explored the implications for existing records and urged institutions to consider the amount of resources that might be required to implement. It was suggested that LC could choose not to implement, but others should have the benefit of being able to use a subfield specifically for form subdivisions. However, it is not clear that it would be desirable or even possible for a new subfield for form to be defined in the USMARC standard without LC using it, particularly since LC is the major originator of subject authority records for LCSH. The discussion resulted in a request that LC prepare a proposal to define subfield $v in the Bibliographic 6XX fields with accompanying additions to Authority 1XX fields. In addition, an Authority 18X subdivision field would be needed. Participants suggested that consideration be given to a proposal to include a new field 155 in the Authority format complementary to field 655 (Index Term--Genre/Form). It was also requested that LCSH plans for using the new subfield be stated in the proposal, especially in terms of use of field 655. In order for the impact of such a major change to be assessed, a questionnaire was distributed on the USMARC discussion list. A MARBI member is compiling the results of the questionnaire and will post them on the USMARC list before the current proposal is discussed at the February meetings of the USMARC Advisory Group. The questionnaire addressed the following issues: Amount of time needed to validate new fields/subfields Types of changes needed to system for new field/subfield Need for and timing of retrospective conversion A possible algorithm to be used by systems for conversion Possible improvements to system if subfield $v were available In an earlier discussion of this issue (Discussion Paper No. 74: Defining a New Subfield Code for Form Subdivisions in the USMARC Bibliographic/Authority/Classification/Community Information Formats) there was no consensus as to whether or not a retrospective conversion of bibliographic and authority records would be necessary if the new subfield is defined. It had been noted that, if a thesaurus has clear rules as to what is a form subdivision, such a conversion would be possible to accomplish. Conversion of LCSH strings could prove problematic in many cases, although, generally, form subdivisions appear as the last subfield in a string. Thus, programs could be designed to catch most but not all subdivisions in LCSH strings. If a conversion is not done, records will be inconsistent, and display and search results could be confusing. The survey does attempt to deal further with this issue. 2. DISCUSSION Form data have been defined by the Subject Analysis Committee as follows: "Form data are those terms and phrases that designate specific kinds or genres of materials. Materials designated with these terms or phrases may be determined by an examination of: - their physical character (e.g., videocassettes, photographs, maps, broadsides) - the particular type of data that they contain (e.g., bibliographies, questionnaires, statistics) - the arrangement of information within them (e.g., diaries, outlines, indexes) - the style, technique, purpose, or intended audience (e.g., drama, romances, cartoons, commercials, popular works) - or a combination of the above (e.g., scores) A single term may be modified by other terms, in which case the whole phrase is considered to be form data (e.g., aerial photographs, French dictionaries, conversation and phrase books, wind ensemble suites, telephone directories, vellum bound books, science fiction)." The following are reasons why it was considered desirable to define a new subfield code for form subdivisions by SAC and the Subject Subdivisions Conference. - to facilitate compression of online displays in online public access catalogs by allowing for the general categorization of subdivisions of the focus term by form as well as by geographic, chronological, and general subdivision - to make displays in online catalogs more helpful listings of headings - to allow for greater precision in searching - to reduce the number of authority records required so that separate records are not required for every topic-form pair - to provide more effective machine manipulation for database maintenance and validation. It would allow for machine validation systems to ignore form subdivisions - information in the new form subfield could easily be moved to field 655 (Index Term--Genre/Form) at a later date if agencies decide to make more widespread use of that field Concept-based display. It has been noted that most catalog users do not look past the first screen when browsing in specified subject terms in a library catalog. Currently, one of the many obstacles in the way of effective subject access in online catalogs is the excessive length of the index display under a specified search term. It has been argued that browsing large subject indexes could be more effective if subdivisions were grouped conceptually, rather than alphabetically, to provide further definition of the original concept. A compressed, conceptually- based display would summarize the scope of the library's collection on a particular topic in a single screen by consolidating subdivided headings into categories. In 600-651 fields, form subdivision information could be distinguished from general subdivision information by defining a new subfield $v specifically for form information. This would allow for a display with greater flexibility. A general message for all records subdivided by a particular subfield code could be substituted, which would vastly reduce the size of index displays. For instance, in the case of the $z subfield code for geographic subdivision, text in the index display could be a phrase such as "subdivided by geographical area" (e.g., Islam and politics-- SUBDIVIDED BY GEOGRAPHICAL AREA, E.G. AFGHANISTAN). The same could be said for subfield code $y and the new subfield code for form. A user could thus use such information to decide to further search or to not search such information. Example of such a display: English literature -- SUBDIVIDED BY CHRONOLOGICAL PERIOD English literature -- SUBDIVIDED BY FORM OR TYPE OF MATERIAL English literature -- SUBDIVIDED BY GEOGRAPHIC AREA It should be noted, however, that with LCSH strings, such an abbreviated display reflects only the nature of the subdivisions at the level of the first subdivision. Selecting and viewing English literature -- SUBDIVIDED BY FORM OR TYPE OF MATERIAL does not retrieve all instances of form subdivisions in strings that begin with English literature. Strings with English literature subdivided by geographic or chronological subdivisions may themselves have additional form subdivisions. However, whether display designers and system vendors will make more use of subfield coding with the addition of a new subfield $v has been questioned. Distinguishing dual functioning subdivisions. How to control dual functioning subdivisions in authority records also needs to be considered. It may be a problem for systems that validate against an authority file to control the dual functions of these subdivisions if the subdivision is sometimes coded as $x and other times as $v. If authority records are created for subdivisions, those subdivisions that may function either as a general subdivision or as a form pose a choice: would the subdivision be established as a 180 field (Heading--General Subdivision) or a new field 183 (Heading--Form Subdivision)? These issues need to be resolved before any implementation. Theoretically, most form subdivisions can also function as topical subdivisions. For example the subdivision periodicals usually functions as a form in a subject heading string, indicating that the work is a periodical on a particular topic. For instance "United States -- History -- Periodicals" is used for a periodical about United States history. "Periodicals" can also function as a topical subdivision as in "Chemistry -- Periodicals -- History", for a work about the history of periodicals in the field of chemistry. Another example of a dual functioning subdivision in LCSH is Folklore. It is used as a form subdivision to identify folklore texts, e.g. collections of tales or legends of a group of people. It is also used as a general subdivision to identify works that discuss the folklore of particular topics or groups of people. For instance, Indians of North America -- Folklore is used for texts of their legends or discussions about them. If the subdivision were distinguished by subfield coding, the following two examples are possible: 650 $aIndians of North America $vFolklore [For collections of folklore of North American Indians] 650 $aIndians of North America $xFolklore [For discussions about the folklore of North American Indians] In this case, both subdivisions occur at the end of the string. Conversion of existing records. If the new subfield is defined and a retrospective conversion is deemed desirable, existing records could be converted through a global update using the list of form subdivisions in the particular thesaurus. The following explores a possible algorithm and how it might be applied; it appeared in the Form subdivision survey, initially distributed in September on the USMARC list: "By retrospective conversion, I am referring to a special project to identify form subdivisions in subfield $x of subject headings in existing files and then move them to subfield $v of the same subject heading. Such a conversion may need to be performed on all databases. To undertake such a conversion, your computer program would need several lists, such as: - a list of approved form subdivisions for each subject thesaurus. - a list of dual-function subdivisions if applicable for a specific thesaurus. A computer algorithm summarized as follows might be used: (1) In 600-651 fields, look for occurrence of terms which match those present on the list of approved form subdivisions for the specific thesaurus. If found, continue to next step. (2) Check the term against the list of dual-function form subdivisions if available for the specific thesaurus. If there is a match, print out the information for human review and editing. Otherwise, continue to next step. (3) Check to see if the term is the last subfield in the field. If this is the case, change the subfield delimiter from $x to $v. If this is not the case, print out the information." Training requirements. Subject thesauri systems will have to provide documentation as well as revise existing documentation to guide catalogers in the correct assignment of subfield codes for form subdivisions. Training and retraining of catalogers will be needed. 3. POSSIBLE LIBRARY OF CONGRESS IMPLEMENTATION The Library of Congress recognizes the need to distinguish form data in bibliographic records in order to manipulate it for display, retrieval, and validation of headings. However, debate continues about the best place to record and store form data in MARC bibliographic records-- whether to retain it in separately coded subfields of subject heading strings, to remove it to a separate field, such as the 655, or to employ a combination of methods. LC feels that further study needs to be undertaken to determine the optimum method. Currently, LC uses the 655 field in limited situations in its bibliographic records. LC needs to develop a comprehensive plan for using the 655 field with LCSH. Application of a new subfield code to identify form subdivisions in LCSH depends upon LC's ability to provide a list of form subdivisions that identifies those that may also function as topical subdivisions, and to provide clear instructions for coding them. The best way to handle authority records for dual functioning subdivisions in the LC Subject Authority File needs to be determined before LC can implement a new subfield code. Should they be coded in the authority record as $v with an indication that they can also function as $x, or would two authority records be needed, one with the subdivision in an $x and one with it in a $v? Could systems handle records having identifcal text that is coded differently? After these issues are resolved, LC plans to implement a new subfield code for form subdivisions in current cataloging if this proposal is approved. Possible retrospective conversion of LC's bibliographic database could only be considered within the context of other pending automation projects and after global update is implemented. 3. RELATED ISSUES The following issues need to be considered as part of this proposal. Results of the survey, which will be compiled and distributed on the USMARC list prior to ALA, may assist in arriving at decisions. 1. Retrospective conversion * Would it be necessary to convert existing records to use the new subfield for form subdivision? Does it make sense for some systems to convert and others not to? * If there is no retrospective conversion, what would be the implications for searching and display of a file that is mixed, with earlier records using $x for form subdivisions, and later records using $v? Would it make the displays more confusing if no conversion were done? 2. Use of subfield $v * Is it a possible solution to only use $v in certain thesauri (e.g., MeSH, AAT)? Could LCSH be excluded or could it be implemented for LCSH on a limited basis? How might this type of solution be affected by record exchange? 3. Authority control * How will LCSH authority records be controlled for dual functioning subdivisions? * Should LC look at finding ways to eliminate some dual functioning subdivisions? * For systems that check against the authority file, how will machine validation work if form subdivisions are coded in the authority file as such (in subfield $v or in field 183), if in the bibliographic record it is functioning (and coded) as a general subdivision? Should they be always coded in the authority record as $v with an indication that they can also function as $x? Or would two authority records be needed, one with the subdivision in $x and one with it in $v? Could a system handle it if the identical text were in two different records coded differently? 5. PROPOSED CHANGES The following is presented for consideration: - Define subfield $v (Form subdivision) in the following field blocks: 6XX (Bibliographic) 1XX (Authority) 4XX (Authority) 5XX (Authority) 7XX (Classification) 6XX (Community Information Subfield $v will be defined as follows: Subfield $v contains a form subdivision that designates a specific kind or genre of material as defined by the thesaurus being used. Subfield $v is appropriate only when a form subject subdivision is added to a personal name, corporate name, name/title, uniform title, geographic name, topical, or genre heading to form an extended subject heading. Subfield $v is used for form terms when they function as indicated above; the terms are coded in subfield $x if they function as general subdivisions. A form subdivision in subfield $v is generally the last subfield in the string. The subfield may be repeated if more than one form subdivision is used. - Change the definition of subfield $x (General subdivision) in the above fields as follows: Subfield $x contains a subject subdivision that is not more appropriately contained in subfields <$v, (Form subdivision),> $y (Chronological subdivision) or $z (Geographic subdivision). Subfield $x is appropriate in the X00 fields only when a topical subject subdivision is added to a name or name/title heading to form an extended subject heading. - Define fields 183 (Heading--Form Subdivision), 483 (See From Tracing--Form Subdivision), 583 (See Also From Tracing--Form Subdivision), 783 (Subdivision Linking Entry--Form Subdivision) See Attachment A for a list of fields requiring the changes if the new subfield code for form were approved. See Attachment B for a possible description and examples of subfields $x and $v. See Attachment C for a possible description of field X83. ------------------------------------------------------------------ ATTACHMENT A Bibliographic format 600 Subject Added Entry--Personal Name 610 Subject Added Entry--Corporate Name 611 Subject Added Entry--Meeting Name 630 Subject Added Entry--Uniform Title 650 Subject Added Entry--Topical Term 651 Subject Added Entry--Geographic Name 654 Subject Added Entry--Faceted Topical Terms 655 Index Term--Genre/Form (the form in subfield $a is a genre or form and it can also be subdivided in a subfield $x by a general subdivision) 656 Index Term--Occupation 657 Index Term--Function 755 Added Entry--Physical Characteristics Authority format 100 Heading--Personal Name 110 Heading--Corporate Name 111 Heading--Meeting Name 130 Heading--Uniform Title 150 Heading--Topical Term 151 Heading--Geographic Name 180 Heading--General Subdivision 181 Heading--Geographic Subdivision 182 Heading--Chronological Subdivision 400 See From Tracing--Personal Name 410 See From Tracing--Corporate Name 411 See From Tracing--Meeting Name 430 See From Tracing--Uniform Title 450 See From Tracing--Topical Term 451 See From Tracing--Geographic Name 480 See From Tracing--General Subdivision 481 See From Tracing--Geographic Subdivision 482 See From Tracing--Chronological Subdivision 500 See Also From Tracing--Personal Name 510 See Also From Tracing--Corporate Name 511 See Also From Tracing--Meeting Name 530 See Also From Tracing--Uniform Title 550 See Also From Tracing--Topical Term 551 See Also From Tracing--Geographic Name 580 See Also From Tracing--General Subdivision 581 See Also From Tracing--Geographic Subdivision 582 See Also From Tracing--Chronological Subdivision Classification format 700 Index Term--Personal Name 710 Index Term--Corporate Name 711 Index Term--Meeting Name 730 Index Term--Uniform Title 750 Index Term--Topical 751 Index Term--Geographic Name 754 Index Term--Faceted Topical Terms Community information format 600 Subject Added Entry--Personal Name 610 Subject Added Entry--Corporate Name 611 Subject Added Entry--Meeting Name 630 Subject Added Entry--Uniform Title 650 Subject Added Entry--Topical Term 651 Subject Added Entry--Geographic Name 651 Subject Added Entry--Geographic Name 654 Subject Added Entry--Faceted Topical Terms 656 Index Term--Occupation 657 Index Term--Function ------------------------------------------------------------------ ATTACHMENT B (From field X00 in USMARC Authority Format) [ ] indicates deletion; < > indicates addition <$v - Form subdivision Subfield $v contains a form subdivision that designates a specific kind or genre of material as defined by the thesaurus being used. Subfield $v is appropriate only when a form subject subdivision is added to a personal name, corporate name, name/title, uniform title, geographic name, topical, or genre heading to form an extended subject heading. Subfield $v is used for form terms when they function as indicated above; the terms are coded in subfield $x if they function as general subdivisions. A form subdivision in subfield $v is generally the last subfield in the string. The subfield may be repeated if more than one form subdivision is used. 100 0#$aGautama Buddha$vBiography$vEarly works to 1800 100 3#$aClark family$vFiction > $w - Control subfield [400/500] Subfield $w contains up to four character positions (designated as $w/0, $w/1, etc.) that indicate whether special instructions apply to the display of the heading and whether a tracing is restricted to the reference structure of a particular type of authority. Subfield $w is appropriate only in the 400 See From Tracing and 500 See Also From Tracing fields. Guidelines for applying the codes defined for subfield $w are provided in the Tracing and Reference Fields -- General Information section. $x - General subdivision Subfield $x contains a subject subdivision that is not more appropriately contained in subfields <$v, (Form subdivision),> $y (Chronological subdivision) or $z (Geographic subdivision). Subfield $x is appropriate in the X00 fields only when a topical subject subdivision [or a form subject subdivision] is added to a name or name/title heading to form an extended subject heading. 100 1#$aBrunhoff, Jean de,$d1899-1937$xCharacters$xBabar [100 0#$aGautama Buddha$xBiography$xEarly works to 1800] 100 1#$aTatlin, Vladimir Evgrafovich,$d1885-1953.$tMonument to the Third International $xCopying 100 0#$aNapoleon$bI,$cEmperor of the French,$d1769-1821 $xAssassination attempt, 1800 (December 24) 400 1#$aWashington, George,$d1732-1799$xExpedition, 1753-1754 $y - Chronological subdivision Subfield $y contains a subject subdivision that represents a period of time. Subfield $y is appropriate in the X00 fields only when a chronological subject subdivision is added to a name or name/title heading to form an extended subject heading. 100 1$$aShakespeare, William,$d1564-1616$xCriticism and interpretation$xHistory$y18th century ------------------------------------------------------------------ ATTACHMENT C USMARC Authority Format X83 Form Subdivisions -- General Information 183 Heading -- Form Subdivision (NR) 483 See From Tracing -- Form Subdivision (R) 583 See Also From Tracing -- Form Subdivision (R) Indicators First Undefined # Undefined Second Undefined # Undefined Subfield Codes Subdivision term portion $v Form subdivision (R) $y Chronological subdivision (R) $x General subdivision (R) $z Geographic subdivision (R) Tracing and linking subfields $i Reference instruction phrase [483/583] (NR) $w Control subfield [483/583] (NR) $5 Institution to which field applies [483/583] (NR) $6 Linkage (NR) GUIDELINES FOR APPLYING CONTENT DESIGNATORS The content designators identify the subelements occurring in form subdivision headings constructed according to generally accepted thesaurus-building conventions (e.g., "Library of Congress Subject Headings, Medical Subject Headings"). A form subdivision is used as a subdivision portion of an extended subject or index term access field in bibliographic records. A form term that is used as the lead element of an established heading record is contained in a 150 (Heading -- Topical Term) field. The content designators defined for field 783 (Subdivision Heading Linking Entry -- Form Subdivision) in the first indicator position and the subdivision term portion and control subfield $6 are described in this section and are not repeated in the field 783 description. The content designators unique to the heading linking entry fields are described in the 7XX Heading Linking Entries -- General Information section. INDICATORS Both indicator positions are undefined; each contains a blank (#). SUBFIELD CODES $i - Reference instruction phrase [483/583] Subfield $i contains a reference instruction phrase other than those that may be system generated from the field tag or from the codes defined for subfield $w (Control subfield). Subfield $i is appropriate only in the 483 See From Tracing and 583 See Also From Tracing fields. Guidelines for applying subfield $i are provided in the Tracing and Reference Fields -- General Information section. $w - Control subfield [483/583] Subfield $w contains up to four character positions (designated as $w/0, $w/1, etc.) that indicate whether special instructions apply to the display of the heading and whether a tracing is restricted to the reference structure of a particular type of authority. Subfield $w is appropriate only in the 483 See From Tracing and 583 See Also From Tracing fields. Guidelines for applying the codes defined for subfield $w are provided in the Tracing and Reference Fields -- General Information section. $v - Form subdivision Subfield $v contains a form subdivision that designates a specific kind or genre of material as defined by the thesaurus being used. 183 ##$vFiction 040 ##$aDNLM#cDNLM 183 ##$vcase studies$vsoftware $x - General subdivision Subfield $x contains a subject subdivision that is not more appropriately contained in subfields $v, (Form subdivision), $y (Chronological subdivision) or $z (Geographic subdivision). Subfield $x is appropriate in the X00 fields only when a topical subject subdivision is added to a name or name/title heading to form an extended subject heading. Subfield $x contains a topical or language subdivision term. Subfield $x is appropriate in an X83 field only when a general subdivision is added to a form subdivision to form an extended subdivision heading. $y - Chronological subdivision Subfield $y contains a subdivision term that represents a period of time. Subfield $y is appropriate in an X83 field only when a chronological subdivision is added to a form subdivision to form an extended subdivision heading. $z - Geographic subdivision Subfield $z contains a geographic name subject subdivision. Subfield $z is appropriate in an X83 field only when a geographic subdivision is added to a form subdivision to form an extended subdivision heading. $5 - Institution to which field applies [483/583] Subfield $5 contains the USMARC code for the organization that has added a tracing field to a national authority file record. Subfield $5 is appropriate only in the 483 See From Tracing and 583 See Also From Tracing fields. Guidelines for applying subfield $5 are provided in the Tracings and Reference Fields -- General Information section. $6 - Linkage Subfield $6 contains data that link pairs of fields that are alternate graphic representations of each other. It contains the tag number of an associated field and an occurrence number. A complete description of subfield $6 and guidelines for applying it are provided in the 882 Alternate Graphic Representation section. INPUT CONVENTIONS Punctuation The punctuation of the subelements of a heading is generally dictated by subject heading system/thesaurus rules. These input conventions clarify USMARC punctuation practices. An X83 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. One space is used after an open-ended date when it is followed by another subfield. One space is used between the final period of an abbreviated term and a word that follows. Display Constant -- [dash associated with the content of subfield $v, $x, $y, or $z] The dash ( -- ) that precedes a subject subdivision heading is not carried in the USMARC record. It may be system generated as a display constant associated with the content of subfield $v, $x, $y, or $z. Use of subfields $x, $y, and $z For LCSH, subfields $x (General subdivision), $y (Chronological subdivision), and $z (Geographic subdivision) are unlikely to be used in conjunction with field X83, since the form subdivision would generally not be followed by another subdivision when it is functioning as a form. RELATED USMARC FIELD OR DOCUMENT 7XX Heading Linking Entries -- General Information 783 Subdivision Heading Linking Entry -- Chronological Subdivision 880 Alternate Graphic Representation Tracing and Reference Fields -- General Information