First, some real-world examples of "<名詞>、それは<名詞句>。" :
- イノセンス、それはいのち (catchphrase for the movie イノセンス)
- リゾートホテル、それは[極上]{ごくじょう}のサービスに[心]{こころ}[満]{み}たされる[空間]{くうかん} (catchphrase used by a certain resort hotel)
- 歓{よろこ}び。それはBMW。 (catchphrase for the Japanese market used by BMW)
Is it correct to say that these are formed by "left dislocation" and "体言止{たいげんど}め"?
For instance, the underlying sentence of the first example, I think, is
イノセンスはいのちだ
"Dislocation" is a grammatical term describing a sentence structure in which one constituent is taken out of its normal place of occurrence, either to the left side or the right side. The dislocated element's original place is often occupied by a pronoun. (Heavily drawn from Wikipedia.) For example, "These things, they take time."
Applying left dislocation turns the sentence into:
イノセンス、それはいのちだ
"体言止め" is a figure of speech in which a sentence is terminated by a noun or a noun phrase.
イノセンス、それはいのち
All seem nice and well, but I'm not sure because I couldn't find any source talking about this construct in any way. Is the hypothesis correct, or am I missing something? Are there other possibilities?
Edit:
I did find this chiebukuro Q&A which states the English equivalent of the construct is "extraposition." It lists examples like "The demands, restrictions, pressure, fatigue, ― they spoiled the fun." Inferring from this comment to a Language Log entry, this type of extraposition is now classified as left dislocation.
So...whatever the grammatical term is, there's one supporting view that a transformation is in the work here which extracts the topic and places it outside the normal sentence structure.