How do I make items optional in ?

Question

I have such xsd. These all fields can exist or not and in unpredictable order.

Answer 1

You need to put the minOccurs on the individual elements, not the <xs:all>, i.e.

<xs:all>
    <xs:element ref="field1" minOccurs="0"/>
    <xs:element ref="field2" minOccurs="0"/>
    <xs:element ref="field3" minOccurs="0"/>
    <xs:element ref="field4" minOccurs="0"/>
    <xs:element ref="field5" minOccurs="0"/>
</xs:all>

Putting minOccurs="0" on the <xs:all> is saying that entire group may be omitted, not individual elements.

See XML Schema docs.

Answer 2

try like this in all

 <xs:element ref="field4" minOccurs="0" >