The essence of subclassing is the ability to represent classification hierarchies reflecting domain concepts. With the right class mechanism there is no need for a separate type/subtype mechanism, and general classes may have behavior specifications so that subclassing also implies code reuse. Sometimes the application is so well defined (known) that developers may readily start out with classes that represent domain concepts. Singular objects have been around for some time, so a new kind of language with equal support for both objects and classes would simply ask for tool support for objects in the spirit of e.g. Self and support for classes as described above.