Given  school #1: contains attributes of name and district
<?xml version="1.0" encoding="utf-8"?>
<School name="Joy" district="Albany">
<Class>A</Class>
<Teacher>Dave</Teacher>
</School>


school #2: missing district attribute; but has additional attribute of
principle
<?xml version="1.0" encoding="utf-8"?>
<School name="Happy" principle="Joe">
<Class>B</Class>
<Teacher>Mary</Teacher>
</School>


I want to have an identity copy without "Class" element.  I think
following would work:


<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">


     <!-- Identity transformation -->
     <xsl:template match="@*|node()">
         <xsl:copy>
             <xsl:apply-templates select="@*|node()"/>
         </xsl:copy>
     </xsl:template>


   <!-- Omit Class -->
     <xsl:template match="Class"/>
</xsl:stylesheet>


Also, I want to ensure every school must have name and district
attribute; a school can have additional attribute as original as well.
And the district attribute is forced to have same value of "NY".


That is, running the school #1, I would expect following:
<?xml version="1.0" encoding="utf-8"?>
<School name="Joy" district="NY">
<Teacher>Dave</Teacher>
</School>


And running the school #2, I would expect following:
<?xml version="1.0" encoding="utf-8"?>
<School name="Happy" district="NY" principle="Joe">
<Teacher>Mary</Teacher>
</School>


Now, the question is how can I enhance the stylesheet above to do the
attribute manipulation task?