A KB that uses XML entities, such as in the code below, will validate in oXygen and be parsed and queried correctly by OO jDREW, but will fail OO jDREW validation.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE doc [
<!ENTITY xs "http://www.w3.org/2001/XMLSchema">
<!ENTITY xsi "http://www.w3.org/2001/XMLSchema-include">
<!ENTITY ruleml "http://ruleml.org/spec">  
<!ENTITY metax "http://athant.com/metax">  
]>


<RuleML xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns="http://ruleml.org/spec"
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://ruleml.org/spec http://www.ruleml.org/1.0/xsd/hornlog.xsd">
  <!-- RuleML Axiom Schema stating that everything in the domain 
       satisfies the predicate http://athant.com/metax/vocab#Thing .-->
  <Assert>
    <Atom closure="universal">
      <Rel iri="&metax;/vocab#Thing?rel"/>
      <Var>X</Var>
    </Atom>
  </Assert>
</RuleML>