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