6.12

Consider the following lattice structure of generalization and specialization (attributes are not shown).

For entity sets $A$, $B$, and $C$, explain how attributes are inherited from the higher level entity sets $X$ and $Y$. Discuss how to handle a case where an attribute of $X$ has the same name as some attribute of $Y$.

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$A$ inherits all the attributes of $X$, plus it may define its own attributes. Similarly, $C$ inherits all the attributes of $Y$ plus its own attributes. $B$ inherits the attributes of both $X$ and $Y$. If there is some attribute name which belongs to both $X$ and $Y$, it may be referred to in $B$ by the qualified name $X$.name or $Y$.name.