How to ignore the validation of Unknown tags?

Question

One more challenge to the XSD capability,

I have been sending XML files by my clients, which will be having 0 or more undefined or [call] unexpected tags (May appear in hierarchy). Well they are redundant tags for me .. so I have got to ignore their presence, but along with them there are some set of tags which are required to be validated.

This is a sample XML:

<root>
  <undefined_1>one</undefined_1>
  <undefined_2>two</undefined_2>
  <node>to_be_validated</node>
  <undefined_3>two</undefined_3>
  <undefined_4>two</undefined_4>
</root>

And the XSD I tried with:

  <xs:element name="root" type="root"></xs:element>
  <xs:complexType name="root">
    <xs:sequence>
      <xs:any maxOccurs="2" minOccurs="0"/>
      <xs:element name="node" type="xs:string"/>
      <xs:any maxOccurs="2" minOccurs="0"/>
    </xs:sequence>
  </xs:complexType

XSD doesn't allow this, due to certain reasons.
The above mentioned example is just a sample. The practical XML comes with the complex hierarchy of XML tags ..

Kindly let me know if you can get a hack of it.

By the way, The alternative solution is to insert XSL-transformation, before validation process. Well, I am avoiding it because I need to change the .Net code which triggers validation process, which is supported at the least by my company.

Answer 1

In case your not already done with this, you might try the following:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="root" type="root"></xs:element>
  <xs:complexType name="root">
    <xs:sequence>
      <xs:any maxOccurs="2" minOccurs="0" processContents="skip"/>
      <xs:element name="node" type="xs:string"/>
      <xs:any maxOccurs="2" minOccurs="0" processContents="skip"/>
    </xs:sequence>
  </xs:complexType>
</xs:schema>

Under Linux this works fine with xmllint using libxml version 20706.

Answer 2

Conclusion:

This is not possible with XSD. All the approaches I was trying to achieve the requirement were named as "ambiguous" by validation-tools, accompanying bunch of errors.