Help with XSD Schema

Question

XSD

Hello, there is such a code: Although I indicated that appearance is not necessary, the check does not pass. Why doesn't minOccurs="0" work in this case?
<xsd:element name="clientin" minOccurs="0" maxOccurs="1">
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:maxLength value="15" />
<xsd:minLength value="15"/>
<xsd:pattern value="(IIN|BIN){0,1}(\d){12}"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:element>

Answer 1

Use nillable="true", that's when the element can be omitted.
You can also read http://www.dimuthu.org/blog/2008/08/18/xml-schema-nillabletrue-vs-minoccurs0/