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States
•Roles and States are similar.
•Both reflect the ‘situation’ a thing is in.
–e.g. Order may be similar to Person as an Entity
•An Order could play the ‘role’ of (or be in the state of) “Pending”, “Sold”, “Rejected”, “Returned”, etc.
Generally, an Entity could ‘play’ many Roles. An Entity playing a Role is often in one State.
Of course, this is arguable where we can say something is in many ‘states’. However, a state is often ‘viewed’ from a particular context. That is, from one stakeholder context, it’s in one state.
Also, states can be derived. E.g. an Order cannot be Returned without having been Sold.