[jdt-dev] Definition and purpose of IPackageFragmentRoot IPackageFragmen

[Alexander Wirz <alexwirz@xxxxxx>]

Hello!
Can somebody tell me the exact definition of IPackageFragmentRoot and 
IPackageFragment?
As far as I know an IPackageFragment can be a package with classes or a 
package containing sub-packages. Why it is called IPackageFragment and 
not IPackage? Another question: why IPackageFragmentRoot doesn't contain 
a method like getPackageFragment()? What is the dependence between 
IPackageFragmentRoot and IPackageFragment?
I hope I asked not to many questions at once ;-)
Thank you in advance and please excuse my bad english ;-)