ISO/IEC 13249 defines a number of packages of generic data types common to various kinds of data used in multimedia and application areas, to enable that data to be stored and manipulated in an SQL database. The package in each subject area is defined as a part of ISO/IEC 13249. This part of ISO/IEC 13249 defines those concepts, notations and conventions that are common to two or more other parts of ISO/IEC 13249. In particular, it describes the way ISO/IEC 9075 is used in other parts of ISO/IEC 13249 to define the user-defined types and their behaviour appropriate to each subject area.