1<schema xmlns="http://www.ascc.net/xml/schematron" >
2     <pattern name="Attributes present">
3          <rule context="BBB">
4               <assert test="not(@aaa) or (@aaa and @bbb)">The element must not have an isolated aaa attribute</assert>
5               <assert test="not(@bbb) or (@aaa and @bbb)">The element must not have an isolated bbb attribute</assert>
6          </rule>
7     </pattern>
8</schema>
9