No Untyped references
Any reference to a URI in any context other than as the object of an annotation property must have a type triple for that URI. https://github.com/dallemang/fibo/blob/da/hygiene2/etc/testing/hygiene/testHygiene1.sq
Crossing domains / ranges
If one property is a sub of another, then the domains (respectively ranges) should not be subClasses in the opposite direction. https://github.com/dallemang/fibo/blob/da/hygiene2/etc/testing/hygiene/testHygiene2.sq