In the previous chapter we looked at how to select individual headings for an item. Nearly all of the headings were pre-coordinated combinations of two or more concepts such as Chocolate factories or Equine dentistry, and indeed it can be hard to find headings that represent only simple concepts. Even so, in the case of more complex subjects, a series of headings is usually necessary to cover all the various aspects of the subject. In many cases complicated subjects can be expressed more elegantly by structured or composite headings rather than by a list of individual headings.

The nature of structured headings

Although cataloguers cannot invent headings, they can build extended headings using subdivisions provided as part of LCSH. (In Classification Web the subdivisions are held in a separate database from the main headings, and can be searched for independently.) The subdivisions are added to the main headings, subject to certain rules and constraints. These extended headings may be referred to as structured headings since they consist of more than one component or element. Like many other features of LCSH, structured headings can only be created according to the LCSH rules, and you should not be tempted to invent new ones by analogy.

For the most part, structured headings of this kind are not routinely included in the published LCSH, although you will come across some examples. This means that there are very many potential headings that individual cataloguers can create as needed.

Sometimes structured headings can become very complicated, with five or six elements, although a combination of two or three is more common. Typical examples of structured headings are:

Bells–Collectors and collecting

Cosmetics—Additives

Morse code–Problems, exercises, etc.

Organometallic chemistry–Nomenclature–Handbooks, manuals, etc.

Parapsychology and crime–Case studies

Perpetual calendars–Belarus—Periodicals

Books and reading–England–Northumbria (Region)–History –To 1500—Sources

It feels somehow more satisfying to express a compound subject with a compound heading, and a single heading of this type seems to me essentially better than a list of unconnected headings, since it provides a succinct statement of the content of a document.