Why didn't they use Core Data entity inheritance?

[malhal]

You have to wonder why Apple didn't just use Core Data for this sample. That gives composed data sources for free via entity inheritance. Could have saved them 1000 lines of code or so. It seems a recurring issue in Apple examples where you have a developer highly experienced in one framework but has no experience of another, and leads to these weird examples trying to rewrite stuff into a way they understand rather than just learning the framework. The Advanced NSOperations is another example.