Understanding Tags and Fields

A field contains a piece of data that makes up a portion of a MARC record. A tag is a three‑digit number that identifies the type of information in its corresponding field. (For example, tag 245 identifies the main title information; tag 020 identifies the ISBN number.) MARC rules define what information a tag identifies. Most tags that contain the digit “9” designate local or customized information. The term “tag” is sometimes used to designate an entire piece of information, including the three‑digit number, the indicator, and all the subfields.

Horizon provides a defined list of MARC tags. When you want to add a tag to a record, you can open the list to choose a valid tag. You can also add a tag by opening a new line and entering the tag number manually. (For more information, see Adding a Component to a MARC Record.)

You can use SHIFT+F1 from a valid MARC tag or subfield to link directly to the Library of Congress web site where that tag is explained. Your system administrator can change the link so that it finds a different URL. (For instructions, see “Setting Up or Changing Valid MARC Record Components” in the Cataloging Setup Guide.)

A MARC record contains these types of fields:

Fixed Fields. Fixed fields are often called control fields. They are divided into positions. Each position contains information about the record in abbreviated form. The information in a fixed field can fill only the predefined length of the field. Fixed field positions have a valid set of values or codes defined by MARC standards.

Note: Use caution when editing fixed fields. Most information is specific as set by MARC standards. Anything you change or delete should conform to the applicable standards.

Variable Fields. Variable fields can contain varied lengths of information, as specified by the MARC cataloging rules that your library follows.

Variable fields can be linking or nonlinking:

Linking fields. These fields include authority‑controlled, bib‑to‑bib, URL, multimedia, and other linking fields. The authority‑controlled fields contain information from the authority record (author, subject, or series) to which the bib record is attached. (For example, tag 100 is an authority‑controlled tag that displays the main author.) Other linking fields contain information that relates to the item (such as a URL, electronic data, or a sound file) that the field links to.
Nonlinking fields. These fields contain information about the bib record that is not from another record or associated with another item. (For example, tag 245 is a nonauthority‑controlled tag that displays the title.)

You can have these kinds of variable fields:

Type of variable field

What the field displays

Authority‑controlled linking

Information about an author, subject, or series title that Horizon has stored in a separate “authority” record

Bib records link to the authority record to get uniform information for these fields.

Authority‑controlled nonlinking

Information about an author, subject, or series title that should be uniform, but from which Horizon does not link to an authority record

The data should be reviewed to find a link or create a new authority record from it.

Nonauthority‑controlled linking

Information other than an author, subject, or series title, but that links to something such as another bib record, a URL, or an electronic document

Nonauthority‑controlled nonlinking

Information other than an author, subject, or series title that does not link to anything else

 


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