A data element is the basic unit of identifiable and definable metadata information. It is formed from putting together a data element concept, and a value domain. In other words, it’s a description of what information is being collected (the data element concept), and the way it’s being measured (the value domain).
A data element can be thought of as ‘an entry on a form’ that someone has to fill out, on behalf of a person or an organisation, to report data to a central authority or governing body. Data elements are gathered into groups, or data set specifications, to form complete sets of data about a particular topic.
As an example, Establishment—neurosurgical unit indicator, yes/no code N is a data element recording whether an establishment, a medical facility of some sort, has a neurosurgery facility or not. The value domain in this case is simply the answer Yes or No.
A lot of data elements refer to people. For example: Prison entrant—legal status of prisoner, detention status code N. This data element allocates a code for the legal status of a person entering prison. There are three possible answers in this case: Remand, Sentenced, or Unknown.