Remember, GLS approaches are not database dependent as are LNAV/VNAV approaches. GLS is similar to ILS as the approach geometry is send out by the ground station. It is however often combined with low RNP segments in intermediate approach or for the missed approach segment, and those are of course database stuff.
Whaaaaat? Can I get a source for that info?
As far as I've understood, in airports where it is in use, like in EDDW, the GLS channel selected determines the GBAS station to be used for GPS correction and nothing more - the actual approach info still comes from the FMC....
Edit: Okay, I should check first before asking stupid questions - in any case, I guess some system has to perform the deviation checking - and I doubt its the MMR but rather the FMC. I'll shut up now - sorry folks