Seymour Lubetsky wrote in 1969 that “the book…comes into being as a dichotomous product–as a material object or medium used to convey the intellectual work of an author.” This dichotomy between the physical book and the intellectual work is at the center of Resource Description and Access. From this insight has arisen a hierarchy of bibliographic entities (more on this word later) that attempts to “comprise the products of intellectual or artistic endeavor that are named or described in bibliographic records” (FRBR, 13). The entities that make up this hierarchy are called work, expression, manifestation, and item—or WEMI for short. Any resource may be considered at any stop along this hierarchy. The work is the intangible intellectual product; the expression is the physical realization—using alphanumeric symbols, for example—of the work; the manifestation is a particular embodiment of an expression; an item is a single, physical instance of a manifestation.
Let’s see how this works in practice. Take a well-known book, Pride and Prejudice by Jane Austen:
The work is Pride and Prejudice, as fully conceived in the mind of Jane Austen.
The expression is the realization of the work in, for example, text or spoken word. There are many ways a work can be expressed, and it can be difficult to determine what constitutes a separate expression, and what is a new work entirely; cataloger judgment is required. In general, translations, revisions, versions, illustrated editions, abridgements, and illustrated editions would be considered unique expressions of the same work. So a translation of Pride and Prejudice into Russian would be considered an expression of the work Pride and Prejudice. An illustrated version (in some cases) would be a new expression. If Austen had revised her novel, the revised version would be a separate expression as well. An annotated version of the work would also probably be considered a separate expression, as long as the annotations substantially change the expression (i.e., not just a couple of footnotes; if, however, the annotations are extensive and are considered the major part of the work, then it may constitute a separate—but related—work). An abridged version would probably be a separate expression, but a summary or adaptation (as, for example, a film version of Pride and Prejudice) would be its own separate work. Pride and Prejudice and Zombies would obviously be a separate work, though related to Pride and Prejudice by being a satire of it. Most works will have only one or two expressions—a text version and a spoken word version, say—but a great classic like Pride and Prejudice is likely to have many expressions.
An example of a manifestation is Pride and Prejudice, published by Penguin Books in 1989, with an ISBN number of 834935764-0. A single expression may have many manifestations, especially if (as with Pride and Prejudice) the book is frequently reprinted. Catalogs traditionally have separate records for separate manifestations.
The item is the book on the shelf, with a particular barcode, provenance, and circulation history.
Work, expression, manifestation, and item are all defined by Functional Requirements for Bibliographic Records as entities. FRBR defines a total of 11 entities, separated into three groups. Group 1 entities are those described above: work, expression, manifestation, and item. Group 2 entities are person, corporate body, and family. Group 3 entities are concept, object, event, and place. (These groups correspond to the traditional title-author-subject catalog divisions.)
Any one of these entities can have multiple attributes and can also have relationships with other entities. Another way to think of RDA is thus as a large entity-relationship model, composed of entities, their attributes, and the relationships between them. Let’s see what this means in practice. A work (entity) is created by (relationship) a person (entity) with particular birth and death dates (attributes). The work (entity) is also realized through (relationship) one or more expressions (entities), which in turn are embodied in (relationship) manifestations (entities), each of which is published by (relationship) a publisher (entity) located at a particular address (attribute). In addition, the work (entity) may be an adaptation of (relationship) another work (entity) and may have another expression (entity) as its supplement (relationship). And so forth. RDA’s goal is to record all these entities, attributes, and relationships. Visit www.rdatoolkit.org/background for many entity-relationship diagrams related to RDA. See “Relationship designators” below for more information on how RDA records relationships between entities.