Answer:
enumeration constraint.
Step-by-step explanation:
Enumeration constraints is a definition term or tag in programming language, that is used in assigning values to variables in order to generate partial solutions, so as to remove from the constraint network the conflicting values that do not lead to any feasible solution.
For example: not xs:element or xs:sequence
Here, using enumeration constraints, to limit the content of an XML element to a set of acceptable values:
The example below defines an element called "music_genre" with a restriction. The only acceptable values are: Blues, Reggae, Country:
Hence:
Using not xs:element
<xs:element name="music_genre">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="Blues"/>
<xs:enumeration value="Reggae"/>
<xs:enumeration value="Country"/>
</xs:restriction>
</xs:simpleType>
</xs:element>