What does [文] as in "[文]のに対して" stand for?


I stumbled on this grammar formula in the 日本語総まとめＮ３ book: "[文]のに対して", but I'm
not sure what [文] stands for. Does it mean a sentence? If it is a sentence, it
should end in either N/A/Na/V in 普通形 form, so according to the formula, this
should be legit:

> 田中先生は生徒だのに対して厳しい。

but is it really grammatically correct? The book also writes "Nに対して" and its
example is:

> 田中先生は生徒に対して厳しい.  
>

This [文] part really confuses me, and the book doesn't explain what it stands
for, even though it appears a lot in the book. Please help me!




～のに対して basically means _whereas_ which connects two "sentences". Here are some
examples:

  * 田中先生は優しいのに対して、木村先生は厳しい。
  * 田中先生は高齢であるのに対して、木村先生は若い。
  * 田中先生は英語ができるのに対して、木村先生はできない。

So the phrases before のに look like legitimate 文, don't they?

「田中先生は生徒だのに対して厳しい」 makes little sense because it doesn't connect two
sentences. (Actually this sentence may make sense because [だの happens to mean
"things like
～"](http://dictionary.goo.ne.jp/jn/138101/meaning/m0u/%E3%81%A0%E3%81%AE/),
but let's forget about this for now)

This の in のに対して is actually a nominalizer, and [the general grammatical rule
for the
nominalizers](http://people.uncw.edu/kanoy/practices/NominalizersKotoNo.htm)
is applied. That means you cannot put everything that looks like a sentence.
For example, 「田中先生は高齢だのに対して、木村先生は若い。」 is ungrammatical.

* * *

**EDIT** : As you can see in this N3 sample question, `[文]` does not always
look like a legit 文 (短気な is the dictionary form of a na-adjective, but you
have to say 父は短気だ in a real 文, of course). So you should understand this `[文]`
as "a nominalize-able phrase which sometimes (but not always) looks like a
sentence."

[![enter image description
here](https://i.stack.imgur.com/KMP80.png)](https://i.stack.imgur.com/KMP80.png)

