I haven't yet tried it, but I would try it like this...
<Value algorithm="wt.rule.algorithm.AndTest">
<Value algorithm="wt.rule.algorithm.IfNotNullTest">
<Attr id="NameEN"/>
</Value>
<Value algorithm="wt.rule.algorithm.IfNotNullTest">
<Attr id="NameDE"/>
</Value>
</Value>
<"If true"/>
<"if false"/>