A name–value pair, also known as an attribute–value pair, key–value pair, or field–value pair, is a fundamental data representation in computer systems and applications. Designers often desire an open-ended data structure that allows for future extension without modifying existing code or data. In such situations, all or part of the data model may be expressed as a collection of 2-tuples in the form <attribute name, value> with each element being an attribute–value pair. Depending on the particular application and the implementation chosen by programmers, attribute names may or may not be unique.
Common examples include JSON objects such as database records where a column maps to a stored value (e.g., username → johndoe), HTTP headers like Content-Type: text/html, and configuration files with settings expressed as settingType=1.