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6xx Fields

6xx Introduction

6xx fields

Use 6xx fields to provide subject access points. Most 6xx fields contain subject access points based on the thesaurus or subject heading system identified in the 2nd indicator or in subfield ǂ2.

Subject access points are assigned to a bibliographic record to provide access according to established subject cataloging principles and guidelines. Use to describe the content of the cataloged resource. Genre/form terms describe what a cataloged resource is, not what it is about.

Use fields 600, 610, 611, 630, 647, 648, 650, 651, 654, and 662 to provide subject access points to a bibliographic record.

Use fields 653, 655, 656, 657, and 658 to provide index terms to a bibliographic record.

Use fields 690, 691, 696, 697, 698, and 699 to provide local subject access to a bibliographic record.

Use field 695 to locally assign added class numbers to a bibliographic record.

For information on coding subject access points in bibliographic records, see Subjects--General Information.

Input standards

If you are creating full-level records, add subject access points for resources that normally require subject access points. If you are creating minimal-level records, optionally add subject access points. You are encouraged to enter at least one subject access point. Prefer terms from established subject schemes.

Fields 690, 691, 695, 696, 697, 698, and 699 do not remain in the WorldCat record, so you must enter appropriate subject access points in fields 600, 610, 611, 630, 647, 648, 650, 651 to meet full-level requirements.

Subject authorities

OCLC defines indicator values and subfield coding for 6xx fields to indicate the subject thesaurus or scheme to which the subject access point belongs. Use the following subject heading schemes or thesauri:

  • Library of Congress Subject Headings (LCSH)
  • LC subject headings for children's literature contained in the "Children's and Young Adults' Cataloging Program" (CYAC) section of LCSH
  • Medical Subject Headings (MeSH)
  • National Agricultural Library (NAL) subject authority file
  • Canadian Subject Headings (CSH)
  • Répertoire de vedettes-matière (RVM)
  • Subject headings or terms based on other subject authorities specified in subfield ǂ2

Constructing 6xx fields for names and titles

For current cataloging, create subject access points for names and titles in fields listed below using descriptive cataloging instructions as appropriate in accordance with a subject heading scheme. If applying LCSH, search the LC/NACO Authority File and use the established forms of names and preferred titles found there. If not found, construct the access point according to RDA or AACR2. For original cataloging in other subject heading schemes, search applicable authority files and use the established forms of names and preferred titles found there. If not found, construct the access point according to the instructions appropriate for the subject scheme used.

For information on retrospective cataloging, see Chapter 2.3, Transcribing Cataloging Copy.

Constructing 6xx fields for topics, places, etc.

For access points in other other subject 6xx fields, use the appropriate thesaurus. If the subject access point is not derived from a standard thesaurus, but it has value to institutions other than yours, include the subject access point with 2nd indicator 4, but only if no other subject access points derived from a standard thesaurus are present.

Constructing 6xx fields for index terms

For access points in index term 6xx fields, use the appropriate thesaurus. Use field 653 to record terms that are not derived from controlled subject heading lists.

Constructing 6xx fields for local subject access points

For access points that are nonstandard and useful only for your institution, use the fields below, which are not retained in WorldCat records:

Constructing 6xx fields for classification

For an added class number assigned to materials in classified catalogs, use field 695. For each added class number, use a separate 695 field, which is not retained in the WorldCat record.

FAST headings

FAST (Faceted Application of Subject Terminology) is derived from the Library of Congress Subject Headings (LCSH), one of the library domain’s most widely used subject terminology schemas. The OCLC Research project, searchFAST provides users an interface to simplify the process of access point selection.

For each WorldCat bibliographic record with Library of Congress Subject Headings (LCSH) and no FAST headings, OCLC adds a set of FAST headings using the FAST conversion algorithm. After the initial set is added, the FAST headings are maintained field by field, regardless of whether the fields were entered by a user or by the FAST algorithm.

FAST Maintenance

Adds. Periodically, the FAST headings in bibliographic records are compared to the FAST headings that would be generated from the LCSH in the record by the conversion algorithm. New fields generated by the algorithm are added to the record. No FAST headings are deleted by this process since existing fields reflect fields previously added by the algorithm or by users.

Changes. When an authorized access point in the FAST Authority File changes, all bibliographic records with the access point are updated with the replacement. Periodically, WorldCat is scanned to identify and correct minor variations in FAST headings, e.g., tags and indicator values are corrected, and subfield ǂ0 values are converted to a standard form or added if missing.

Deletes. When an authorized FAST heading splits into two or more fields, the FAST heading is deleted from the corresponding bibliographic records because it is not possible to automatically determine which replacement field should be used. FAST headings for undifferentiated personal names removed from the LC/NACO Authority File are also deleted from bibliographic records.


For more information, including content designator history, see MARC 21 Format for Bibliographic Data, 6xx.

This page last revised: August 29, 2020