| 4.7 User-defined types |
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| A user-defined type is a schema object, identified by a <user-defined type name> . The definition of a userdefined type specifies a number of components, including in particular a list of attribute definitions. Although the attribute definitions are said to define the representation of the user-defined type, in fact they implicitly define certain functions (observers and mutators) that are part of the interface of the user-defined type; physical representations of user-defined type values are implementation-dependent. |
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| The representation of a user-defined type is expressed either as a single data type (some predefined data type, called the source type), in which case the user-defined type is said to be a distinct type, or as a list of attribute definitions, in which case it is said to be a structured type. |
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| A user-defined type is described by a user-defined type descriptor. A user-defined type descriptor contains: |
| - The name of the user-defined type (<user-defined type name> ). This is the type designator of that type, used in type precedence lists (see Subclause 9.5, "Type precedence list determination"). |
| - An indication of whether the user-defined type is a structured type or a distinct type. |
