DM means more than simple drag and drop in that sense, that it can manage object hierarchies in arbitrary depth. The basic approach for the implementation of these classes was to keep them as small and as simple as possible. Unlike the NIH or other class libraries they implement only the most important features of their Smalltalk equivalents, thus they are very small, easy to port and to use.
All classes are prepared to support persistence in two different ways.
The third way to make object data persistent - using relational databases.