There is a big specification big gap regarding the content found in the Avalon Context. The pure Avalon approach is that you always have the right stuff since this part of the IOC approach. Consequently there is now way to check for the existence of a name/value pair. On the down side each Avalon container has its own ideas about the variable name to use resulting in non-reusable Avalon services.
YAAFI use a pragmatic approach to provide all Merlin and Fortess names in the context. Therefore is should be easy to use existing Fortress services within YAAFI. It is also a good idea to stick to the Fortress names leaving you the option to switch Avalon containers in the future.
YAAFI allows to decommision an Avalon service programmatically. Since the services are singletons you might ending up with a stale reference. Therefore it is not a good idea to decommision services you keep a reference on ... :-). In the case your application design depends on such a feature you should lookup the decommissioned service again resulting in creating a brand new instance.