CIDs, ContractIDs and IDL files...

[Darin Fisher]

I have a simple question about IDL files.  It seems that all throughout
the mozilla source, IDL files contain CIDs, ContractIDs, and often
factory methods in %{C++ %} blocks.  These things correspond to a
particular implementation of the interface (or, in the case of
ContractIDs, to a particular class of implementations), right?  So, then
why are they listed in the IDL files?  Isn't this wrong?  Why do the
IDL files list stuff identifying a particular implementation?

Thanks,
Darin