ignoring elements order in xml validation against xsd

Question

Hi,

Ia processing an email and saving some header inside a xml document. I also need to validate the document against a xml schema.

As the subject suggest, I need to validate ignoring the elements order but, as far as I read this seems to be impossible. Am I correct?

If I put the headers in a<xsd:sequence>, the order obviously matter. If I us <xsd:all> the order is ignored but for some strange reason this imply that the elements must occur at least once.

My xml is something like this:

<headers>
  <subject>bla bla bla</subject>
  <recipient>[email protected]</recipient>
  <recipient>rcp02domain.com</recipient>
  <recipient>[email protected]</recipient>
</headers>

but I think the final document is valid even if subject and recipient elements are swapped.

There is really nothing to do?

Answer 1

Yes, it is possible. Just create a choice (in some type or element content model, of course) with maxOccurs set to unbounded.

<xs:element name="headers">
    <xs:complexType>
        <xs:choice maxOccurs="unbounded">
            <xs:element name="subject" type="xs:string"/>
            <xs:element name="recipient" type="xs:string"/>
        </xs:choice>
    </xs:complexType>
</xs:element>

Answer 2

First, some requirement guessing:

• "subject" is mandatory
• At least one "recipient" is mandatory

Since you have only two different elements it is very easy to accomplish it:

<xs:element name="headers">
<xs:complexType>
 <xs:choice>
   <xs:sequence><!-- The recipient MUST be after the subject -->         
     <xs:element name="subject" type="xs:string" />
     <xs:element name="recipient" minOccurs="1" maxOccurs="unbound" type="xs:string" />
   </xs:sequence>
   <xs:sequence><!-- The recipient is before the subject -->          
     <xs:element name="recipient" minOccurs="1" maxOccurs="unbound" type="xs:string" />
     <xs:element name="subject" type="xs:string" />
     <xs:element name="recipient" minOccurs="0" maxOccurs="unbound" type="xs:string" />
   </xs:sequence>
 </xs:choice>
</xs:complexType>
</xs:element>