Validate xml if any one element exists in a sequence xsd

Question

I have the following XSD:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
 <xs:element name="PaymentSearchRequest">
  <xs:complexType>
     <xs:sequence>
        <xs:element name="User">
           <xs:simpleType>
              <xs:restriction base="xs:string">
                 <xs:minLength value="1" />
              </xs:restriction>
           </xs:simpleType>
        </xs:element>
        <xs:element name="Password" nillable="false">
           <xs:simpleType>
              <xs:restriction base="xs:string">
                 <xs:minLength value="1" />
              </xs:restriction>
           </xs:simpleType>
        </xs:element>
        <xs:element name="Key" minOccurs="0">
           <xs:simpleType>
              <xs:restriction base="xs:string" />
           </xs:simpleType>
        </xs:element>
        <xs:element name="Iteration" default="0000" minOccurs="0">
           <xs:simpleType>
              <xs:restriction base="xs:short" />
           </xs:simpleType>
        </xs:element>
        <xs:element name="ReturnUrl" minOccurs="0">
           <xs:simpleType>
              <xs:restriction base="xs:anyURI">
                 <xs:minLength value="1" />
                 <xs:pattern value="[hH][tT]{2}[pP]://[wW]{3}.*" />
              </xs:restriction>
           </xs:simpleType>
        </xs:element>
        <xs:element name="PaymentSearch" maxOccurs="unbounded">
           <xs:complexType>
              <xs:sequence>
                 <xs:element name="SessionId">
                    <xs:simpleType>
                       <xs:restriction base="xs:string">
                          <xs:minLength value="5" />
                       </xs:restriction>
                    </xs:simpleType>
                 </xs:element>
                 <xs:element name="ConfirmationNumber" minOccurs="0" >
                    <xs:simpleType>
                       <xs:restriction base="xs:string" />
                    </xs:simpleType>
                 </xs:element>
              </xs:sequence>
           </xs:complexType>
        </xs:element>
     </xs:sequence>
  </xs:complexType>
</xs:element>
</xs:schema>

This was working fine with our old business logic. And the following XML was being validated:

<PaymentSearchRequest>
    <User>[email protected]</User>
    <Password>test@1</Password>
    <PaymentSearch>
        <SessionId>79C14E66-87E1-42BD-9974-096E2D037D22</SessionId>
        <ConfirmationNumber />
    </PaymentSearch>
</PaymentSearchRequest>

Now I need to cater the following scenarios:

1)

<PaymentSearchRequest>
    <User>[email protected]</User>
    <Password>test@1</Password>
    <PaymentSearch>
        <ConfirmationNumber>HUS73945KJAF</ConfirmationNumber>
    </PaymentSearch>
</PaymentSearchRequest>

2)

<PaymentSearchRequest>
    <User>[email protected]</User>
    <Password>test@1</Password>
    <PaymentSearch>
        <SessionId>79C14E66-87E1-42BD-9974-096E2D037D22</SessionId>
    </PaymentSearch>
</PaymentSearchRequest>

3)

<PaymentSearchRequest>
    <User>[email protected]</User>
    <Password>test@1</Password>
    <PaymentSearch>
        <SessionId>79C14E66-87E1-42BD-9974-096E2D037D22</SessionId>
        <ConfirmationNumber>AJKF3894KJ3425</ConfirmationNumber>
    </PaymentSearch>
</PaymentSearchRequest>

What I have tried so far:

Choice element The choice element approach is failing for the third scenario.

Answer 1

The following xsd using xs:choice and successfully validate all of the 3 possible PaymentSearch scenarios you posted :

<xs:element name="PaymentSearch" maxOccurs="unbounded">
   <xs:complexType>
      <xs:choice minOccurs="1" maxOccurs="unbounded">
         <xs:element name="SessionId">
            <xs:simpleType>
               <xs:restriction base="xs:string">
                  <xs:minLength value="5" />
               </xs:restriction>
            </xs:simpleType>
         </xs:element>
         <xs:element name="ConfirmationNumber">
            <xs:simpleType>
               <xs:restriction base="xs:string" />
            </xs:simpleType>
         </xs:element>
      </xs:choice>
   </xs:complexType>
</xs:element>

You can change maxOccurs of xs:choice to 2 if each of ConfirmationNumber and SessionId can only occur once (so that maximum occurrence of the two is 2).