Longwinded example follows, thanks in advance to anyone that makes it through the whole thing, let alone feels nice enough to respond:

Let's say I've got an item hierarchy derived from a class called NamedObject. NamedObject is really just an abstraction for a named entity in my domain. The base class has a parent property (pointing to another NamedObject) and the subclasses on the tree have children collections specific to each subclass. For example:



Ideally what I'd like is to use a <joined-subclass> here for a new type derived from Server called ServerConnectionDetails that should map to it's own table. I'd like a single column that's a PK/FK in this new table like <joined-subclass> does but NHibernate is complaining here about my mapping file, it looks like I can't have a <joined-subclass> child of a <subclass> element.

So I guess there's no way to set up a hybrid inheritence tree like this? If not, what's the next best way to go about this, or is there a cleaner way of doing what I'm attempting? I believe I need the NamedObjects table like I have it or else the code for the bulk of the functionality of my application gets incredibly ugly.

I think your design is already ugly. you should implement the Composite pattern. AFAIK you can't implement mixed inheritance trees with hibernate. as joined-subclass is in fact using the one-to-one relationships, you can have a protected property in your implementation pointing to that table(class) and delegate to that class.

HTH,
radu