Assuming we have tables something like:
car-map-feature
that relates features to cars... many-to-many.
We'd like to say car.features or feature.cars.
Could the relation specification system accommodate some general
specification for essentially giving an alias for an arbitrary path walking
a chain of relations.
Kinda like a macro - the alias expands to its 'primitive' relations.
Similarly... order.shipments, product.buyers, etc
And of course, we'd like to put constraints on any of the intermediate
tables, perhaps also through another alias.