ImportPackageXMI() for importing a root node

[Anderl]

I'm using ImportPackageXMI() for importing an XMI file. While this works well when importing beneath a package, I haven't been able to import the XMI as a root node. Is this impossible via the automation interface? The first parameter to ImportPackageXMI() is the GUID of the package to import into, which obviously doesn't exist for a root node.