XML Schema Complete Reference, The

6.11. Instantiability

Not all element types are instantiable in an XML instance. Element types may directly prohibit the existence of corresponding instances. Similarly, a complex type functioning as the structure type of an element type may indirectly prohibit the existence of corresponding instances. This section illuminates restrictions on instantiability of element types, attribute types, simple types, and complex types.

6.11.1. Element Type Instantiability

An element type is explicitly non-instantiable when the element type‘s representation specifies the abstract attribute with a value of ‘true’. An element type may be implicitly non-instantiable due to its structure type being explicitly or implicitly non-instantiable.

Section 8.2 discusses ...