Name–value pair
In such situations, all or part of the data model may be expressed as a collection of 2-tuples in the form
Depending on the particular application and the implementation chosen by programmers, attribute names may or may not be unique.
As a result, they are not fully general; they cannot be used, for example, to implement electronic mail headers (which are ordered and non-unique).
Some data serialization formats such as JSON support arbitrarily deep nesting.
[2] Other data representations are restricted to one level of nesting, such as INI file's section/name/value.
