Nominal and Structural Subtyping in Component-Based Programming
By: Klaus Ostermann
In nominal type systems, the subtype relation is between names of types, and subtype links are explicitly declared. In structural type systems, names are irrelevant; in determining type compatibility, only the structure of types is considered, and a type name is just an abbreviation for the full type. We analyze structural and different flavors of nominal subtyping from the perspective of component-based programming, where issues such as blame assignment and modular extensibility are important.