Homework answers / question archive / For this lab: Lab 3 - Apply the lab 2 feedback on your Lab 2 ER/EER diagram

For this lab: Lab 3 - Apply the lab 2 feedback on your Lab 2 ER/EER diagram

Computer Science

Share With

For this lab: Lab 3 - Apply the lab 2 feedback on your Lab 2 ER/EER diagram. - Normalize the ER/EER diagram of Lab 2 and make a NER diagram (Normalized ER Diagram).To do please follow the instructions of normalizing an ER/EER diagram attached here.

Normalizing the ER Diagram:

• What we did so far is ER diagram (ER). In order to do ER, our only concern is to capture right entities with right attributes and right relationships between entities. Also we like to figure out the general cardinality of relations.
• After we are done with ER, it is time to do some normalization. We can break the process of normalization into two steps. First step is to normalize attributes, and second step is to normalize relationships between entities.  

NER Step 1:

• Attribute Normalization is the process of turning compound attributes and multivalued attributes into entities and establish a relation between these new entities and the base entity.
• This is the ER of the bookstore that we have: 
• For the first step of normalization we focus on compound attributes such as publisher. We turn them into entities and establish a relation between them and the base entity. In our example Publisher is a compound attribute: 
• Now let’s do the same thing for multivalued attributes. Multivalued Attribute becomes a separate relation with a foreign key taken from the superior entity.
• Then we focus on composite attributes such as name and address. Use only their simple, component attributes:  

NER Step 2: 

• On Step 2 of normalization we focus on relationships:
  • Any many-to-many (M-N) relationship should be turned into an associative entity.
  • We have to switch the cardinality of the original relation when we break it into a pair of relationships.
  • Since associative entity is an entity after all, we have to use a proper name for them. We cannot simply use the Verb that used to be the name of the original relation for associative entity.
• The notation for associative entities is a diamond inside a rectangle; in other word it is the mix of relation symbol and entity symbol.
• The normalized ER (NER) diagram: