Replace “ISA” constructs with identifying relationship sets

This is the most popular method for restructuring generalizations/specializations, because:

1. it is the method that best preserves the original hierarchical representation,
2. it may always be applied.

One operates as follows:

1. one removes the “ISA” construct,
2. one transforms every child entity set into a weak entity set,
3. one draws an identifying relationship set (formally with 1:1 cardinality) between each newly created weak entity and what was the father entity set

Notice that the newly created weak entity sets are peculiar in that they do not present a discriminator.

Exercise:

1. Restructure the diagram as described above.
2. Click at compare with solution to verify your result.

M3.02 E-R Restructuring