Comment 17 for bug 1749475

Thanks, Dan.

I'm open to dropping the external flag -- we can bring that in when there's a use case ready for it, like external PDF processing. The initial specific reasoning for the flag was to provide a signal that an external XPath 2.0 processor that can make use of extant bibliography XSLTs will be called and that some special (though currently undefined) handling of the template output may be necessary.

The holdings flag lets us leverage one definition mapped with different settings -- params won't allow that. Looking at it through the lens of the targeted use case(s) in the offered code, I can see how it looks use-case specific, but even if we were dealing with definitions with different hook core types of, say, circulations or holds or serial subscriptions, it would have generally the same meaning and IMO could be used to the same general effect.

The sortable flag is more about whether the choice should be presented to the user (allowing a signal to the UI, rather than to the definition as with "holdings"), so I think it belongs at the current level in the stack, but for the current implementation it isn't strictly necessary (sorting always allowed) and I wouldn't fight too hard to keep it.