<P> In IDEF1X, a government standard for capturing requirements, possible sub-type relationships are: </P> <Ul> <Li> Complete subtype relationship, when all categories are known . </Li> <Li> Incomplete subtype relationship, when all categories may not be known . </Li> </Ul> <Li> Complete subtype relationship, when all categories are known . </Li> <Li> Incomplete subtype relationship, when all categories may not be known . </Li>

(ii) explain with examples the concept of strong and weak entities