How to remove elements from an XML instance document that is not partof

["Costello, Roger L." <costello@mitre.org>]

Hi Folks,

Scenario: The XML Schema says the root element is Document and it contains a sequence of an A element followed by a B element. Here's a schema-valid XML instance:

<Document>
    <A>blah</A>
    <B>bar</B>
</Document>

I receive this instance document:

<Document>
    <A>blah</A>
    <B>bar</B>
    <C>oops</C>
</Document>

For the instance to be schema-valid, the C element must be removed. 

Is there a tool that, given an XML Schema and an XML instance, the tool returns the instance minus any invalid elements? That is, the tool returns a schema-valid instance.

/Roger