Works and expressions

Understand these two important concepts.

Two important concepts that are an essential part of the API are works and expressions.

• A Work is a piece of legislation, such as an act, regulation or by-law. A work may be amended over time and may even have its title changed. A work is uniquely identified by a work FRBR URI which never changes.

• An Expression is a version of a Work in specific language at a particular point in time. A work can have many expressions, usually one for each official language and amendment. An expression is uniquely identified by its own expression FRBR URI, which is derived from the work's FRBR URI.

An example of a work is the South African Employment Equity Amendment Act, 2013 (Act 55 of 1998) with unique work FRBR URI /akn/za/act/1998/55. This act has been amended a number of times since it was first passed. Each amended version (also called a point in time) is a unique expression of the work.

The English expression of the work, as it was amended on 17 January 2014, is uniquely identified by the expression FRBR URI /act/1998/55/eng@2014-01-17. You can see that this is built from the work's URI, with a language code eng and the expression date 2014-01-17 included.

When fetching details from the API, you are always fetching details for a particular expression of the work. The expression will also include information related to the expression's work, such as the work's FRBR URI and publication information. Even if you don't specific a particular date for the expression, the API will return the latest expression applicable at the time of the request.

Akoma Ntoso FRBR URIs

The API relies heavily on Akoma Ntoso FRBR URIs, which are described in the Akoma Ntoso naming convention standard.

When we use a URL such as /v3/frbr-uri/ in this guide, the frbr-uri part is a full FRBR URI, such as /akn/za/act/1998/84/eng.