定语从句中的省略问题

Question

大家好，我最近在学定语从句，但是发现了一下一些问题跟大家讨论下，请大家一起学习进步，请不要在网页上摘取大量信息，只要简明扼要回答便可。随便举几个例：
The company,which was established in 1999,is specialized in producing fruit.
我们知道这个句子是对的，是简单的非限制性定语从句。但能不能做以下变形：
1.The company,established in 1999,is specialized in producing fruit.
2.The company that was established in 1999 is specialized in producing fruit.
3.The company established in 1999 is specialized in producing fruit.
4.The company was established in 1999,specialized in producing fruit.
5.The company specialized in producing fruit was established in 1999.
6.The company,specialized in producing fruit,was eatablished in 1999.
（注意established是被动而不是过去）
我的意思是第一个句子中established作非谓语，就像非限制性定语从句省略了关系代词；变成像第二个句子那样的限制性定语从句成立不；如果第二个句子成立，那么第三个句子亦成立因为他只是省略了关系代词.
主动的情况：
例句：The boy standing at the door is my brother.
1.The boy,who stands at the door,is my brother.
2.The boy,standing at the door,is my brother.
还有，这句话是相当于
3.The boy who stands at the door is my brother.
那么，要表达4这个意思该怎么用省略形式呢？
4.The boy who is standing at the door is my brother.

问题较多，心中有答案但不肯定，原理知道但是有些情况总觉得怪怪的，知道其实学英语不用这样但是就是想搞的很清楚，请大家讨论发言，会再加分。

Answer 1

1.The company,established in 1999,is specialized in producing fruit.
2.The company that was established in 1999 is specialized in producing fruit.
3.The company established in 1999 is specialized in producing fruit.
4.The company was established in 1999,specialized in producing fruit
这几句是正确的

但是我觉得5.The company specialized in producing fruit was established in 1999.
6.The company,specialized in producing fruit,was eatablished in 1999.也可以将specialized改成specializing
因为specialize是动词，specializing in是现在分词做定语
specialized是形容词，用在这里就相当于which is specialized in sth
我觉得两者都行

1.The boy,who stands at the door,is my brother.
要改成who is standing at 强调此刻状态

表达4.The boy who is standing at the door is my brother.就是例句2啦

Answer 2

1.如果第二个句子成立，那么第三个句子亦成立因为他只是省略了关系代词？
不是还有一个谓语动词Was吗？原句中的 was established 是指被动语态，第三句怎麽直接加非谓语动词了呢），意义不同的（2，3句不是等同的）
我认为以上有4个句子成立，只不过好像3，4两句不成立吧……

2.1.The boy,who stands at the door,is my brother.
、The boy,standing at the door,is my brother.
这两个句子本身就是现在是了啊，为什么要改成4句呢，硬着样的话，4句要不是错误的，要不就改成第一，三句吧

不过我很支持你的这种精神，学英语是要钻的，也需要多讨论~

Backy

Answer 3

第一句和第三句都对，而且他们是一个句子。第二句也对。
4.The boy who is standing at the door is my brother.可以按照你的想法，省略who is变成The boy standing at the door is my brother.
这是定语从句的特点，可以省略定语从句中的主系结构！
有问题可以直接和我一起探讨！

Answer 4

这些句子都是对的啊,你的问题我不是很明白呢

Answer 5

3和5错误 其他都对 你把句子成分弄清就可以了。