http://www.movielabs.org/creativeworks/model#isPortrayedBy
Property 'is portrayed by'

ObjectProperty

Character

is portrayed by

Contribution and ((has contributor role value Actor) or (has contributor role value Dubbing actor) or (has contributor role value Stunt actor) or (has contributor role value Self) or (has contributor role value Voice actor))

is portrayal of

Identifies the (or a) contribution (with role Actor) that portrays this character

By making the portrayal a relationship between a Character and a Contribution, we avoid the messy implications of having both a class Portrayal and a class Contribution. If you want to think of the portrayal as an instance (an object), it would be the instance of the class Contribution being pointed to by this property.