PM-STA-0020

A State MUST be modelled as a specialisation of the Thing whose lifecycle stage it represents.

Non-normative: formally neat and pedagogically awful. "New Artist is a kind of Artist" is true in the subsumption sense and collides with the everyday reading, where being new is a stage Larry is in, not a kind of thing Larry is. It also sits awkwardly with PM-STA-0010: class membership in the RDFS sense accumulates and never retracts, whereas a lifecycle stage must be left behind.

The specification keeps the subclass notation because it is what the source says. Any product built on this should never show a user the word "subclass"; states should be presented as stages of a lifecycle. The notation is a liability at the surface even though it is sound underneath.