It was our first time to be on a farm .請問to be之文法觀念為何?

1,首先瞭解本句結構，就知道to be 不可省略，還原本句是Being on a farm was our first time.it只是代名詞，真主詞係to be on a farm(遞延主詞) ，為了避免語句頭重腳輕才如此使用，這在英文寫法履見不鮮。

2,本句be 動詞是exist (存在)，屬不及物動詞

3,舉個例子It would be a serious mistake to ignore the warnings on packs of cigarettes.

1. 講述第一次(the first time名詞)幹哪事的較正確說法:
the first time (that) we have/had been on the farm (together) 
~ 我們(一起)身處農場的第一次

a) Presenting as a complete sentence:
We have/had been on the farm (together) "for" the first time. 
~ 我們第一次(一起)身處農場.

b) Referring the event using a pronoun (demonstrative but not dummy pronoun):
It/This/That is the first time we have been on the farm together.
It/This/That was the first time we had been on the farm together.
~ 這/那 是我們(一起)身處農場的第一次.

3. 用possessive代詞去规限成"我們的第一次":
the first time we had been on the farm
= our first time [being] on the farm
the first time we have been on the farm
= our first time [to be / being] on the farm
即是說, 不定式 ("to be") 在意境上是比較適合用于現在式, 如:
This is my first time to travel on a plane.

有點"畫蛇添足"，通常to be是表示"成為"/"作為"一種身份的說法/寫法

就引用你這例句，較為合理的用法是
It was our first time to be farmers.

不過就以這文法/用法來說，作者的含意可能是指：
to be situated on a farm.
身處某個地方的意思。

好像當第一次坐飛機也有人會說：
It is my first time to be on an airplane.
來表示自己身處其中的意義；
而不像一般人說表示作為"交通工具"：
It is my first time travelling on an airplane.

Referring your book by TW Chen--The heart of grammar, we've,
The re-construction of this sentence  with "to be" just means " Participle active" to turn into the completed adjective;-
eg:-be---> having been;
ie:-Re:-The 1st time we "have been" on the farm is a verbal (to be agrees with been).-----20 marks demanded.
eg:-Having been on a farm, our first (time) visit was established.
was established=it was;
It could be rewritten, with the same meaning, as:-
eg:-Our first (time) visit (to the farm) has (was) established.
was established=it was;
"to be" is used with the past participle to form the passive of verbs
eg:-first time visit "was" "established";
eg:-first time visit "is being" "established".
20 marks demanded.

It was our first time * to be on a farm.

這邊to be當不定詞用, 表目標/目地.

我猜你是跟be混淆, 建議別記太多有的沒的xx詞, 直接用例句記下"情境", 下次直接使用:

1. I'm a good guy.  <- 基礎s+v+o句型不多說.
2. Be a good guy.  <- 命令句.
3. To be a good guy.  <- 表目標/目地.
4. Being a good guy. <- 表事實/經驗.