Stage 5: Derive the logical data model
Knobit of Data modelling · K-516 · Skill
Recognises attributes inapplicable to some instances
What it means
Optional attributes that are optional because they do not apply to some instances, not because the value is unknown. A null then means two things, and the attribute cannot be made mandatory where it should be.
How it is assessed
Flags the deficient case and passes the acceptable one. Deficient: Account with interest rate, maturity date and arrears day count, all `required: false` because none applies to a current account Acceptable: Loan Account and Current Account as subtypes with a discriminator; Loan Interest Rate required on Loan Account, with a value-set code for "not yet fixed" (`LOG-013`)
Builds on
- Explains supertype and subtype constraintsK-566 · Knowledge