Does the term "Bruttogeschossfläche" have a precise definition?

Does it include Balconies? Walls? Basement storage unit (Kellar)? A share of any shared areas (not bike room, not laundry room, by the look of it)?

I'm also interested in the term "Wohnfläche".

ETA:

This is perhaps better than what I had originally linked below, a more concise explanation:
http://www.archinnova.ch/d/immobilie...UndGlossar.htm

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Seeing as you are in LU, from the LU Steuerbuch:

http://www.steuerbuch.lu.ch/index/ba...initionen.html

Anrechenbare Geschossfläche, AGF (früher Bruttogeschossfläche, BGF)

Als anrechenbare Geschossflächen gelten die Flächen aller abgeschlossenen Räume, der Voll-, Dach- und Attikageschosse (ohne Untergeschoss). Die Aussenmauern werden nicht erfasst und die ermittelte Fläche mit dem Berechnungsfaktor multipliziert (§§ 9, 10 und 11 PBV).

You can read more here, see 9 and 10:

https://baurecht.lu.ch/-/media/Baure...V.pdf?la=de-CH
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Hopefully one of the EF architects (Helm?) will come along with a better definition or explanation.

For its own it has no precises meaning, same goes for Wohnfläche. You would need a reference to a definition like SIA 416, SIA D 0162, DIN 277, a specific law etc. and also a reference to the version/year for ex. DIN 277:2016.
or a plan where the area is marked like this:
http://www.themetropolitans.ch/theme...on-SIA-416.pdf