(ref.doc)plnot3

Foundations of Object-Oriented Languages
Andrew Black and Jens Palsberg

Some design dimensions:
Specification types versus implementation types
Structural subtyping versus subtyping by name
Shallow versus deep subtyping
Single versus many implementations for each interface
Type inference versus type annotation
Closed world assumption versus open world assumption
Extension versus overriding
Delegation versus inheritance
Object identity
Multi-methods: encapsulation, compositionality, extensibility, abstract types
Meta-object protocols
Concurrency