Anonymous and Named Data Types
Data types can be either anonymous or named. Named types can be used in other parts of the schema.
Anonymous Data Types
Anonymous data types are referenced only once and contain few constraints. These data types are identified by the lack of a type identifier in the element. The use of anonymous types saves the overhead of naming and explicitly referencing elements.
Named Types and Anonymous Types
Simple and custom types can be named so that they can be reused in other places in the schema. Anonymous types are used only within the element in which the definition appears. You are not required to name every custom type that you create. You can omit the cross reference between the element and type for types that are used once for an element.