; Base Animal type
define :animal [
    init: constructor [name :string]
]

; Dog type inheriting from Animal
define :dog is :animal [
    ; ...
]

; Cat type inheriting from Animal
define :cat is :animal [
    ; ...
]

; Lab type inheriting from Dog
define :lab is :dog [
    ; ...
]

; Collie type inheriting from Dog
define :collie is :dog [
    ; ...
]