Dia daoibh! I am wondering if any one can help me understand the difference between a subordinate subject and a subordinate predicate?

On https://www.braesicke.de/kopul5.htm#cadeiiad it says that both
Cé hé an bhean sin?
and
Cé hí an bhean sin?
can be correct depending on whether the é/í is a subordinate predicate or a subordinate subject.
I’m kind of confused about what this means and how it might change the meaning of the sentence depending on which it is?
I understand what a subpredicate/proleptic pronoun is (I think I got that term right), but now I’m kinda confused about how to know when something is a subordinate subject…
Thank you to anyone who can help!

I'd say that cad í an bhean in the only correct phrase.

But there are phrases like is é an áit, is é mo thuairim and others where a feminine noun is referred to by é - apparently not focusing too much on the gender of noun.

David, did you mean to say "I'd say that cé hí an bhean in the only correct phrase."?

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I'm an intermediate speaker of the Corca Dhuibhne dialect of Irish and also have knowledge on the old spelling
Soir gaċ síar, fé ḋeireaḋ thíar

I agree with David, cé hé an bhean seems unnatural to me. That doesn't mean that it's wrong, as Lars definitely knows more about grammar than I do. Maybe it is used in different parts of Ireland more than in others?

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I'm an intermediate speaker of the Corca Dhuibhne dialect of Irish and also have knowledge on the old spelling
Soir gaċ síar, fé ḋeireaḋ thíar

Yes, I meant cé hí an bhean.

Those are a bit different.

is é mo thuairim go… uses é because the pronoun here refers not to the noun but to the go-subordinate phrase that follows, the copular structure is literally “my opinion (subject) is it (subpredicate): that XYZ (predicate)”. The é is subpredicate referring to go…, and clauses of this kind are always referred to with the default pronoun é, never í.

I’d expect í in cases like is í mo thuairim-se an tuairim gur aontaigh gach éinne léi (though even in such cases, I guess, is é mo thuairim would be common under influence of the type above).

I deal with this type here in my Guide to Irish “to be”.

is é an áit is different yet because áit is commonly referred to with masculine pronouns in general.

EDIT: and coincidentally, you’ll often get cad é before feminine stuff because cad é etymologically comes from caide, caidhe (< Old Irish cote) which was independent of gender of the following stuff, but was in early modern language reanalyzed as cad + pronoun and a new form cad í appeared, but the older cad é / caidé, goidé surviving in all contexts too.

If I were to take a COMPLETE shot in the dark, I would assume that the explanation would be something along the lines of this:
Take the dialogue
Cé hí/hé an bhean san?
Máire.
If the feminine pronoun were to be used, then it could be seen as attributing the noun bean, as it is feminine. If the masculine pronoun were to be used, it would be referring to the name, the actual person, Máire, as, since the person is yet unknown, the grammatical gender is assumed to be masculine. Again, this is only a theory, and I have no idea what the actual explanation would be. I am basing this guess off of the logic of similar constructions that are known to be correct, such as the is é mo thuairim (ná) go, were é refers to the actual opinion, not the noun tuairim.

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I'm an intermediate speaker of the Corca Dhuibhne dialect of Irish and also have knowledge on the old spelling
Soir gaċ síar, fé ḋeireaḋ thíar

Actually, yes. This is equivalent to Nolan's Copula of Identification IIa (or was it IIb - whatever the one was that has ná in it), another example of which is "is é ainm a bhí air ná Séadna". The "go" clause can be seen as similar to "ná".

No. Cé hé an bhean doesn't exist, or at least Labhrás hasn't shown 1) that it exists and 2) that is grammatically correct.

I don’t think I’ve seen the cé hé an bhean type myself and I can’t find a single example in Nua-Chorpas na hÉireann, but Graiméar Gaeilge na mBráithre Críostaí for whatever reason says it is common, §3.19:



EDIT: and regarding what I wrote above – note that I was referring to cad é specifically, and not to cé hé which is different.