Constructing URIs

The are three different allowed ways to build URLs to files and directories:

Mixing physical and virtual roots and directories is not allowed. Trying to use the following URIs causes an exception :

// virtual root and physical directories are mixed, Not OK!!! 
String UrlErr1 = "file:///Internal/data/music/MyDir/theme.mp3";
// physical root and virtual directory are mixed, Not OK!!!
String UrlErr2 = "file:///c:/Music/myDir/theme.mp3"