be to do 结构中的不定式还能看作表语吗?譬如:
The economics of the project are still to be considered.
如此的 are to be considered 还算表语吗?
网友的这个句子，不是“系表结构”，而是一种表示以后的结构。
请仔细阅读我下面的具体剖析。
两种不一样的“be +不定式”结构深层剖析：
【问题的提出】以下两组句子，在be之后都是动词不定式，请问它们有什么不同？
第一组：
Her job is to look after the children. 她的工作是照顾这类孩子。
My aim is to start up my own company. 我的目的是开办一家我一个人的公司。
His ambition was to meet his favourite pop star face to face. 他的心愿是，要面对面地见到他所喜欢的时尚歌星。
第二组：
He is to stay here until we return. 在大家回来之前他需要呆在这里。
Such people are to be pitied. 这种人应遭到怜悯。
If we are to succeed, we must rely on the masses. 大家要成功需要依赖群众。
英语中，“不定式作表语”和表以后的“be +不定式”结构，是两个不一样的定义。第一组是“不定式作表语”； 第一组是表以后的“be +不定式”结构。大家用最简单的办法做一不同，请看这两个句子：
Her job is to look after the children. 她的工作是照料这类孩子。
She is to look after the children. 她将要照料这类孩子。（表以后，可能是安排的任务）
这两句话只不过主语不同，其他部分看着完全一样，意思却大不相同，这是为何？
它们看着太相似了，以至于有时很难不同，这确实是一个非常有意思的问题。
Her job is to look after the children. 意为 “她的工作是照料孩子的。” 本句中，is 是系动词，to look after children是不定式作表语。主语和表语可以互换而意思维持不变：To look after the children is her job.
She is to look after the children. 意为“她将要照料孩子。”本句中，is是助动词，跟不定式to look一块，表示以后。由于不是主系表关系，所以is前后两部分不可以颠倒，不能说：To look after the children is she.
问题中的第一组都可以“主表颠倒”，变成：
To look after the children is her work. 照顾这类孩子是她的工作。
To start up my own company is my aim. 开办一家我一个人的公司是我的目的。
To meet his favourite pop star face to face was ambition. 面对面地见到他所喜欢的时尚歌星是他的心愿。
第二组则不能颠倒，由于颠倒后句意逻辑不成立。
【判断规则】A代表“主语”，B代表“不定式”：
“主系表结构”：A is B. 可以说：B is A. （is意为“是”）
“以后时结构”：A is B. 不能说：B is A. （is to do意为“将要做”）
▲关于不定式表以后的深层剖析：
该问题一般语法书都有论述，但大多不够详细。下面详细解释说明：
在不一样的语境中，“be + 动词不定式” 结构可以表示多种不一样的语义。
1、表示“计划”或“安排”。
This line is to be opened to traffic next week. 该线路将在下周通车。
They are to meet at the gate of the school. 他们将在学校门口见面。
2、表示“命令”。一般译为“需要”或“不准”。
No one is to leave the room without permission.
This naughty boy is to stay here until class is over.
3、表示“可能性”。
Are you to pay the debt for your wife?
The lovely puppy is nowhere to be found.
4、表示“意图”或“计划”。一般译为“想要”。
If you are to be there on time, you had better hurry.
If all of us are to remain friendly, we must be sincere with one another.
5、表示“应该”。
You have done so well. You are to be rewarded.
Such nasty questions are to be avoided.
6、表示“不可防止”或“注定发生”，意为“一定”。比如：
Your plan is to be a failure.
The murderer was sentenced to life imprisonment and was never to see his family again.
She did not think too much of her unkind acts. However, they were to be harmful to herself, too.
Tom wasnt worried about his head injury, but it was to be troublesome for him later.
7、表示“期待”。
The actual use of the newly invented equipment is still to be determined.
Henrys appointment with the firm is yet to be /confirm/ied.
8、表示与以后不符或相反的“假设”。
If it were to rain tomorrow, we would not go outing.
Even if you were to take a taxi now, you would not be able to arrive at your destination on time.
▲关于不定式作表语的深层剖析：
该结构说明“不定式是主语的内容或讲解”。主语和不定式的地方可以颠倒，而意思维持不变。比如：
A salesmans job is to seek out customers. 营销推广员的工作是寻求客户。
Her purpose in learning is to be a doctor. 她学习的目的是当大夫。
My only hope is to use her notes. 我唯一的期望是用她的笔记。
His dream is to become an engineer. 他的梦想是以后成为一名工程师。
The trick is to hold your breath while you aim. 技巧就是瞄按时须屏住呼吸。
Our goal is to achieve the maximum of efficiency. 大家的目的是获得最高的效率。
The purpose of a trap is to catch and hold animals. 陷阱是用来捕捉野兽的。
His target is to save $100 a week. 他的目的是每周储蓄一百元。
The only way to do that is to reduce expenses. 做到这一点的唯一方法是降低开支。
His sole motive is to make more money. 他唯一的动机就是多赚钱。
Our only resort is to inform the police. 大家唯一的方法就是向警方报案。
His hobby is to observe things with his telescope. 他的癖好就是用望远镜察看东西。
His ambition is to fly to the moon one day. 他的愿望是有一天登上月球。
Our aim is to make books available to all. 大家的目的是使大伙都能看得到书。
My chief end is to serve my country and my people. 我的最重要目的是为国为民服务。
Her wish is to go abroad for advanced study. 她的心愿是到海外进修。
One of my duties is to file the letters. 我的职责之一是将信件归档。
Our thought is to avoid war. 大家的意向是防止战争。
My idea is to climb the mountain from the north. 我的想法是从北面登上这座山。
What Tom wants is to do his field work. 汤姆想的是作他的野外实习。
The new managers job is to restore the company to profitability. 新经理的工作是让这家公司能恢复盈利情况。
Her work is to look after the children. 她的工作是照顾这类孩子。
My aim is to start up my own company. 我的目的是开办一家我一个人的公司。
His ambition was to meet his favourite pop star face to face. 他的心愿是，要面对面地见到他所喜欢的时尚歌星。
这种结构的实质是：be是系动词，be前的主语和be后的表语是同位定义，不定式是主语的内容和讲解，主语总是表示“目的，目的，想法，愿望，喜好，工作，责任，办法”之类的名词。
