Multi-valued Attributes

A multi-valued attribute expresses an array of values for each entity of the entity set it is attached to. It can therefore be transformed into a weak entity set by the same name and related to the original entity set with an identifying relationship set with 1:N cardinality.

A simple attribute is needed for the weak entity set to store the values, that were originally stored into the multi-valued attribute in the dominant entity set. This new attribute will also need to be set as the discriminator of the weak entity set.

The original multi-valued attribute is then deleted.

Exercise:

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

M3.02 E-R Restructuring