<schema xmlns='http://www.ascc.net/xml/schematron'>

	<pattern name='datagrid table'>
		<rule context='bar/foo'>
			<assert test="( (not(((../*)|(../text()[normalize-space()]))[2]))
							 or
							 ((preceding-sibling::*) or (preceding-sibling::text()[normalize-space()])) )">
				Error!
			</assert>
		</rule>
	</pattern>

</schema>