Support user-defined data types
When you create UDTs, you also provide the following routines:
- Support functions that the database server invokes implicitly to operate on the data types
- Cast functions that the database server can invoke implicitly or that users can specify explicitly in SQL statements to convert data from one data type to another
- Optional operator-class functions that extend an index method, such as B-tree or R-tree, to manage the new type
- Optional additional routines that other support functions or the end user can call