how can one make a new item an instance of "X", where "X" is something like a class (in OOP terms), a schema (think XML) or a table structure (think RDBMS) so that it gets (the possibility of having) a given set of properties from the start and can perhaps be validated? It seems to me that without a complex datatype, for instance the entity Berlin will be just an amorphous something, and one will have to turn Berlin into a property to be able to make it a city.
How can one reuse the structure of an existing item as a basis for creating a new, similar item?
At Wikidata:WikiProject Books/Book data model, the data model for a book requires the presence of the property "instance of". This of course is fairly easily understod by humans, but does it mean anything to the framework? And if so, how? It is my understanding that inheritance is not supported. I spent a day reading about Wikibase concepts but still have not found any clear answers.