> models trees quite well. Not quite. Performance is far from acceptable, comparing with the heavily tuned hierarchical DBMSes, and I suspect it won't be easy

> models trees quite well. Not quite. Performance is far from acceptable, comparing with the heavily tuned hierarchical DBMSes, and I suspect it won't be easy to ever overcome it. Overhead is too big. > because a tree is a special case of a relational model There are many applications which do not need a relational part, when everything fits hierarchical model well. Of course, if there is a need to mix both worlds, there is no other choice but to stay within relational model.