UMLR — UML needs standardized default package (or Model)

All elements in UML, except for some top-level packages, must be owned by some other element. This means that people who create models without specifying the owning element chain are creating invalid models, that are incapable of being exchanged.

Some tools automatically supply a default owning package, which makes the model valid. However, the tools do not agree on the owning package name or whether it a <<model>>> (stereotyped package)