schema - XSD: How to validate the XML file according to value of some tag?

Question

I was trying to validate this XML file ... where if

1. <tag1> is "Y" then <tag2> must appear

2. if <tag1> is "N" then <tag2> must not appear ..

   <parent>
     <a>
       <tag1>Y</tag1>
       <tag2>sometext</tag2>
     </a>
     <a>
       <tag1>N</tag1>
     </a>
   </parent>
   

I tried <choice> tag but doesn't seem to work .. :( I have come to conclusion that this feature is not available in XSD ..

Can you guide me atleast some alternative to implement this ? by the way I am using Visual Studio 2005 ..

Answer 1

You cannot validate things like that with XSD.

XML schema is not designed and not intended to check "intra-tag" relationships, e.g. "tag2 must be present if tag1's value is 'Y'" - just cannot be done, sorry.

If you need to check these kind of conditions, you'll have to look at Schematron to do that.