In the bibliographical domain, the Functional Requirements for Bibliographic Records (FRBR) distinguishes between aspects of human creation relevant to different contexts. The FRBR concepts of “work”, “expression”, “manifestation”, and “item” as they relate to digital resources are illustrated in the figure below.
A FRBR “work” is a distinct (intellectual or artistic) creation, such as the picture of the Golden Gate Bridge shown above. Different versions of this picture can exist: for example, a colored and a black-and-white versions. These versions are different FRBR “expressions” of the work. Each version of the learning object can take different forms. For example, the colored version of the picture can be available in different format: a JPG, a PNG, or a GIF. Each of these different embodiments of an expression of a work is referred to as a FRBR “manifestation”. Finally, several copies of the colored version of the picture in JPG format may exist in a number of locations. Each of these copies is a FRBR “item”.
Expressions can also be the different translations in which a work is available (e.g., English, French, Spanish) or the different adaptations available to make a work accessible for people with special needs. Similarly, the concept of manifestation is broader than just the file format of a resource. It is the way a resource is presented (i.e., the way it manifests itself) to a user. For example, a resource can be delivered online via a web page, be adapted to be delivered via a mobile platform, or to be streamed.
Metadata specifications such as Dublin Core typically describe resources at the expression level. This is fine if you want to manage a collection of PDFs in English. You get one metadata record per document. Like other metadata specifications, Dublin Core has an element “relation” that can be used to relate one resource to another (e.g., relate a resource to its translations). So, in principle, such relations can be used to express the fact that metadata records are describing different expressions/manifestations of the same work. In practice, such relations are difficult to use and maintain and, for this reason, are rarely used.
Typically with a repository of digital resources available in different languages and different formats, each format in which a particular language version of a resource is available will be described with a different metadata record. This is potentially problematic because the same information is repeated in multiple metadata records (e.g., all the records describing the different manifestations of a given work have the same title) and duplicate information is known to be more difficult to manage and maintain. This also leads to some unwanted results because, if you search a catalog built with these records, you can potentially get multiple hits for the same resources.
All this favors an approach describing a work, its expressions, manifestations, and items with a single metadata record. We will explore possible solutions in our next post.
Picture of the “Golden Gate Bridge” reproduced with permission of Rondo Fish.