A topic can only have one subject. A topic is the type of the topic which it is the instance of. Subject Identity Point is a resource that either constitutes or indicates a subject. Topics that share indicators share subjects. Topic can have zero, one, many base names, base names can be explicitly scoped, base name can give rise to variants.
Scopes become namespaces for topics.
Two topics in same scope are the same. Terminology Discussion Questions on what syntax we should use. Seemed general agreement that model should be removed. Some said both, but keep them separate. So when you use a resource, you should remember this and use things which work with that type.