The Library of Congress >> Librarians, Archivists >> Standards >> MARC

Concise Formats - 2008 Archive >> Classification >> Introduction

Introduction

This is an ARCHIVED VERSION of the 2008 electronic edition of the MARC 21 Concise Formats. Please see loc.gov/marc/concise/ for the most up-to-date version of the electronic MARC 21 Concise Formats.

The MARC 21 Format for Classification Data is designed to be a carrier for information about classification numbers and captions associated with them. The source of the information is the classification scheme identified in field 084 (Classification Scheme and Edition), subfield $a (Classification scheme code).

Kinds of Classification Records

MARC classification records are distinguished from all other types of MARC records by the presence of code w (Classification data) in Leader/06, Type of record. The MARC 21 Format for Classification Data further identifies three kinds of classification records in 008/06, Kind of record:

• Schedule record − A classification data record in which field 153 (Classification Number) contains a classification number or span from the schedule itself, including a number which has been built from applying add instructions (008/06, code a)
• Table record − A classification data record in which field 153 contains a classification number or span from a table. Table numbers generally cannot stand alone and are intended to be added to a base number to form a synthesized classification number (008/06, code b)
• Index term record − A record in which the 1XX field contains a general explanatory term in field 154 (General Explanatory Index Term) that represents a concept that is not related to one classification number or span (008/06, code c)

Types of Numbers

The MARC classification record is an authority record for the classification number(s) and caption contained in field 153 (Classification Number). Classification numbers with captions may also appear in fields 453 (Invalid Number Tracing) and 553 (Valid Number Tracing). Index term only records contain an index term in field 154 (General Explanatory Index Term) instead of a classification number and caption in field 153. Three types of classification numbers are defined in the classification format and identified in 008/07 (Type of classification number):

• Single number - A single classification number is one classification number; the components of which may be contained in a single or repeatable subfield $a (Single number or beginning number of span) in a record.
• Defined number span - A defined number span is a range of classification numbers with a beginning number contained in subfield $a and an ending number contained in subfield $c (Ending number of span). The numbers between the beginning and ending numbers are defined by a separate table or subarrangement.
• Summary number span - A summary number span is also a range of classification numbers with a beginning and an ending number. The caption contained in subfield $j (Caption) summarizes a topic that is represented by the span in subfields $a and $c. A summary number span is not defined by a separate table or subarrangement; instead, the numbers falling within the span are generally defined separately by their own records.

Classification Number Usage in Bibliographic and Authority Records

MARC bibliographic records may contain classification numbers in fields 050-09X. MARC authority records may contain classification numbers in fields 053 (LC Classification Number) and 083 (Dewey Decimal Classification Number). Classification numbers may be valid, invalid or, in the case of a span, partially valid. A valid classification number may be used in a bibliographic or authority record by itself or with additional letters or numbers. In the case of a span, a portion of it may be used in a bibliographic record. In addition a number that has been synthesized by correctly applying a table, internal subarrangement or add instructions to a classification number or span is considered valid for use in a bibliographic or authority record; a classification record may or may not be created for synthesized numbers or numbers within spans.

A partially valid classification number span is one in which only the beginning or ending number of a span is valid. Only the valid portion may be used in bibliographic or authority records. An invalid number may not be used in a bibliographic or authority record. However, a classification record may be created for an invalid number in cases where the reference information cannot be communicated by a simple 453 tracing because a more detailed reference note is required. Invalid numbers in a 153 field of an invalid record or in a 453 field (Invalid Number Tracing) may not be used in bibliographic or authority records.

Required Classification Data Fields

A classification data record should contain at a minimum the following fields:

• 008   Fixed-Length Data Elements
• 084   Classification Scheme and Edition
• 153   Classification Number
• 154   General Explanatory Index Term

Typographical Conventions

Throughout this document, the following typographical conventions are used:

• 0 - The graphic 0 represents the digit zero in tags, fixed-position character positions, indicator positions, and other places numerics are used. This character must be distinguished from an uppercase letter O in examples or text.
• # - The graphic symbol # is used for a blank in coded fields and in other special situations where the existence of the character blank might be ambiguous. (In most textual examples, the blank is represented in the conventional way, by the absence of a character.)
• $ - The graphic symbol $ is used for the delimiter portion of a subfield code. Within the text, subfield codes are referred to as subfield $a, for example.
• / - Specific character positions of the Leader, Directory, field 008, and subfield $w are expressed using a slash and the number of the character position, e.g., Leader/06, $w/0.
• 1 - The graphic 1 represents the digit one (hex 31). This character must be distinguished from a lowercase roman alphabet letter l (hex 6C) and uppercase alphabetic letter I (hex 4C) in examples or text.
• | - The graphic | represents a fill character in MARC examples. When this mark appears in the left margin, it indicates areas of the text of this document where changes have been made.