1. Consider use of enhanced modelling concepts
Objective is to identify superclass and subclass entity types, where appropriate.
• The modelling of superclasses and subclasses adds more information to the data model, but also adds more complexity as well.
• You will meet superclass and subclass entity types in the next Semester
2. Check model for redundancy
Examine the ER model and check whether redundancy is found, and if it is then remove it from the model.
The three activities in this step are:
• re-examine one-to-one (1:1) relationships;
• remove redundant relationship types;
• consider the time dimension when assessing redundancy.
2.1 Re-examine one-to-one (1:1) relationships
You may have identified two entities that are actually the same.
• The two entities should be merged together. If the primary keys are different, choose one as the primary key and the other as an alternate key
2.2 Remove redundant relationship types
Example of removing a redundant relationship called Rents.
we can tell relationship from lease, so the rents are not necessary.
2.3 Consider the time dimension when assessing redundancy
3. Validate conceptual model against user transactions
Objective is to check that ER model supports the required transactions.
Two possible approaches:
• Describing the transaction.
• Using transaction pathways
4. Review conceptual data model with user
Objective is to review the ER model with the user to ensure that the model is a ‘true’ representation of the data requirements of the organisation (or the part of the organisation) to be supported by the database
标签：redundancy,relationship,Database,redundant,Design,Conceptual,model,types,ER From： https://blog.csdn.net/weixin_72151610/article/details/137107838