Data ___domain

For the former IT company, see Data Domain (corporation).

In data management and database analysis, a data ___domain is the collection of values that a data element may contain. The rule for determining the ___domain boundary may be as simple as a data type with an enumerated list of values.^[1]

For example, a database table that has information about people, with one record per person, might have a "marital status" column. This column might be declared as a string data type, and allowed to have one of two known code values: "M" for married, "S" for single, and NULL for records where marital status is unknown or not applicable. The data ___domain for the marital status column is: "M", "S".

In a normalized data model, the reference ___domain is typically specified in a reference table. Following the previous example, a Marital Status reference table would have exactly two records, one per allowed value—excluding NULL. Reference tables are formally related to other tables in a database by the use of foreign keys.

Simple ___domain boundary rules, if database-enforced, may be implemented through a check constraint or, in more complex cases, in a database trigger. For example, a column requiring positive numeric values may have a check constraint declaring that the values must be greater than zero.

This definition combines the concepts of ___domain as an area over which control is exercised and the mathematical idea of a set of values of an independent variable for which a function is defined, as in Domain of a function.

See also

• Data modeling
• Reference data
• Master data management
• Database normalization

References

1. Loshin, David (2001). Enterprise knowledge management: the data quality approach. Morgan Kaufmann. ISBN 978-0-12-455840-3. Retrieved 19 August 2011.