Knobit of Data modelling · K-522 · Skill

Recognises a polymorphic association

What it means

One reference attribute pointing to different entities depending on the value of a type attribute. There is no single parent, so the relationship has no cardinality, no optionality and no rule, and the physical model cannot declare a foreign key. A specific form of row 6.

How it is assessed

Flags the deficient case and passes the acceptable one. Deficient: Case Note with Owner Id and Owner Type (`ACCOUNT`, `PAYMENT`, `PARTY`) Acceptable: One relationship per parent (Case Note → Account, Case Note → Payment), each with its rule, plus a rule that exactly one is set; or a supertype the parents share, only if they pass row 27's test (`LOG-012` when Owner Id has the `foreign-key` role; review only otherwise)

Builds on

Explains relationship cardinality and optionalityK-567 · Knowledge
Explains attribute domainsK-562 · Knowledge

Needed by

None