You can use the XSL to sort out differences between property names in the document class and in the incoming XML. Here is a simple scenario:
An object store has a document class named "Claim" that has a property named "Agent", whose value is the agent's name. But the incoming XML file stores the agent's name in a property named "CaseHandler" whose value therefore needs to be mapped to the "Agent" property.
If you know that the XML contains the following property:
<?xml version="1.0" encoding="UTF-8"?>
<?FileNetDocClass Claim?>
<Claim>
<CaseHandler>Alice</CaseHandler>
</Claim>
The XSL could map it to a property in the "Claim" document class in the following way:
<xsl:template xmlns:xsl="uri:xsl">
<Claim>
<Agent><xsl:value-of select="Claim/CaseHandler"/></Agent>
</Claim>
</xsl:template>
As a result, the XSL maps the value of the CaseHandler property in the XML to the Agent property in the document class, whenever the document is automatically classified.