Assigning and Constructing Subject Headings

This post is courtesy of 


Major Steps in the subject cataloging process: Principles of SLAM

  • Scan  First, scan the subject-rich portions of the item: Title page, table of contents, preface, introduction, text, bibliography, index, dust jacket, container, label, title screen.
  • Look for  Look for key words and concepts that describe what the resource is about. Is it in a particular form (bibliography, encyclopedia, fiction) – or, beginning to think in terms of LCSH, will this item need a form heading or subdivision? What is the author’s intent? Is there an intended audience or special viewpoint? For example, if you are cataloging legal materials, is the item intended for the legal profession or for the general public? (In LCSH the form subdivision "Popular works" is used to distinguish resources intended for a general audience from those inteded for professionals.)
  • Ask yourself  Ask yourself what the resource is about. Is one topic discussed, or several? If several, are the topics discussed in relation to each other, or separately? Is one predominant? Is there a specific object, product, condition, or phenomenon? Is an action or process involved? Is there a focus on a particular place – will you need a geographic heading or subdivision? Is there a focus on a particular time – will you need a chronological heading or subdivision? Is there a focus on a particular person or other named entity – will you need to have a subject heading for a name?
  • Mentally compose Mentally compose a statement beginning: “This resource is about….”

Translate into LCSH

  • Search LCSH  You may begin directly in LCSH. Follow its "USE" (i.e. "use instead") references to identify the authorized heading for a concept, and consider the approaches shown in "See Also" references. Use the hierarchical reference structure of broader and narrower terms to help you identify the most specific heading for your topic. Scope notes can help you decide whether or not a particular heading should be used for your topic. 
  • Search in library catalogs or utilities (e.g. WorldCat) to find similar items; examine subject headings assigned  You may find it helpful to begin by searching bibliographic records in library catalogs or utilities. Keyword searches can be useful in identifying resources on the same or similar topics, and you can then examine the subject headings that have been applied for ideas on where to begin.
  • Search authority files You may prefer to begin searching for existing subject headings in the authority file of your library's catalog.

Use of subfields in constructing compound headings: 

  • $x:  General subdivisions are used to highlight a particular aspect/subtopic of the main subject heading as being the focus of the resource. Example: Fashion -- History.
  • $z: Geographic features and jurisdictions can play a key role in the contents of a work in terms of location, setting, derivation, or origin, and need to be reflected in the assigned headings. Example: Fashion -- History -- France.
  •  $y: Chronological features further contextualize a work, and should be reflected in the record, particularly when LCSH provides an accepted heading for the time period in question. Example: Fashion -- History -- France -- Second Empire, 1852-1870.
  • $v Assign form subdivisions to represent what the item itself is -- its physical format or the particular type or arrangement of data that it contains, in situations where this information is of note.  Example: Fashion -- History -- France -- Second Empire, 1852-1870 -- Video recordings.

Note that subfields are generally applied in this order, i.e. compound headings are constructed by limiting the scope of the main heading -- first limiting it to a particular subtopic, then by location or by time (or, by location then by time) and only then by form.


Library of Congress best practices:

  • General Rule. Assign headings only for topics that comprise at least 20% of the work (by your own estimation). For a record that represents a collected set, such as a periodical or a multi-part item, assign headings that characterize the general contents of the set as a whole. 
  • Number of headings.  The number of headings that are required varies with the work being cataloged. Sometimes one heading is sufficient. Generally a maximum of six is appropriate.
  • Specificity. Assign headings that are as specific as the topics they cover. Specificity is not a property of a given subject heading; instead, it is a relative concept that reflects the relationship between a subject heading and the work to which it is applied. For example, a heading like Psychology is specific when it is assigned to an introductory book about psychology, but too broad for a book that discusses a particular aspect of psychology (such as a specific condition, or treatment modality).
  • General topic and subtopic. If a work discusses a general topic with emphasis on a particular subtopic, or presents a principle and illustrates the principle with a specific case or example, assign separate headings [in separate 6xx fields] for both the general topic/principle and for the subtopic/specific example (provided that the treatment of the subtopic/specific example forms at least 20% of the work, in your own estimation).
  • Two or three related headings. If a heading exists, or can be established, that represents the two or three topics discussed in a work, and that includes no other topics within its scope, assign the one heading instead of two or three narrower headings. [e.g. one heading for Single parents is preferable to two headings for Single mothers and Single fathers.]
  • Exception to the above: Rule of three. If a general topic is widely understood to contain more than three potential subtopics, and the work being cataloged discusses only two or three of these subtopics but discusses them in depth, assign the appropriate two or three headings rather than the broader heading.
  • Exception to the above: Rule of four. In certain circumstances it may be preferable to assign headings for up to four subtopics of a broad concept, e.g. if a heading covers a broad range and each subtopic forms only a small portion of that whole range.
  • Objectivity. Avoid assigning headings that label topics or express personal value judgments regarding topics or materials. Individual cataloger knowledge and judgment inevitably play a role in assessing what is significant in a work's contents, but headings should not be assigned that reflect a cataloger's opinion about the contents. Consider the intent of the author or publisher and, if possible, assign headings for this orientation without being judgmental.