Data Type Facets

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Data Type Facets

Simple types (both built-in and derived) have facets. A facet is a single defining aspect that helps determine the set of values for a simple type. For example, length, minInclusive, and maxInclusive are common facets for the built-in data types. All of the facets for a simple type define the set of legal values for that simple type.

A facet is defined as an element. Each facet element has a fixed attribute that is a Boolean value. When a simple type is defined, you can prevent derivatives of that type from modifying the value of specified facets. To prevent modification of a facet, add the fixed attribute to the facet and set its value to true.

Facets can only appear once in a type definition except for enumeration and pattern facets. Enumeration and pattern facets can have multiple entries and are grouped together.
Example

The following example shows a simple type with the fixed attribute set to true which prevents the length from having a value other than 7.
Xml
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<xs:simpleType name="Postcode">
<xs:restriction base="xs:string">
  <xs:length value="7" fixed="true"/>
</xs:restriction>
</xs:simpleType>



Source : MSDN