夢は〜を持つことです　VS　夢は〜を持ちたいです


This sentence is from my textbook:

> 私の将来の夢は自分の店を［持つことです／*持ちたいです］。

In other words, it says that 持ちたいです is incorrect in this case.

But since the topic is 私の将来の夢、持ちたい seems like a perfectly suitable response.
Why isn't it?

Is the second sentence maybe saying, "My dream is _to want_ to open my own
store"?




> 1 : 私の将来の夢は **自分の店を持つこと** です。(correct)  
>  2 : 私の将来の夢は **自分の店を持ちたい** です。(incorrect)  
>  3 : 私の将来の夢は **自分の店を持ちたいということ** です。(correct)

The sentence structure of 1 is "A is B" where A and B are nouns or noun
clauses.  
As you know A is 私の将来の夢 and B is 自分の店を持つこと in 1, but 自分の店を持ちたい in 2 is not a
noun.  
To change 自分の店を持ちたい into a noun clause you should add "ということ" to it as in 3.

##

# EDIT

Thanks to Yuuichi Tam's comment, I'll add useful information to my answer.

If you do not stick to "A is B" which is the sentence structure of 1 and you
want to use the expression in the second half of 2 as it is, you'll get a
grammatically correct sentence like 4.

> 4 : 私は将来、 **自分の店を持ちたい** 。 or 私は将来、 **自分の店を持ちたい** です。

4 sounds much more natural to the native Japanese than 3.

If you want to use 夢 by all means in 4, it'll become like 5.

> 5 : 私は将来の夢として **自分の店を持ちたい** 。 or 私は将来の夢として **自分の店を持ちたい** です。




> 1 : 私の将来の夢は **自分の店を持つこと** です。(correct)  
>  2 : 私の将来の夢は **自分の店を持ちたい** です。(incorrect)  
>  3 : 私の将来の夢は **自分の店を持ちたいということ** です。(correct)

The sentence structure of 1 is "A is B" where A and B are nouns or noun
clauses.  
As you know A is 私の将来の夢 and B is 自分の店を持つこと in 1, but 自分の店を持ちたい in 2 is not a
noun.  
To change 自分の店を持ちたい into a noun clause you should add "ということ" to it as in 3.

##

# EDIT

Thanks to Yuuichi Tam's comment, I'll add useful information to my answer.

If you do not stick to "A is B" which is the sentence structure of 1 and you
want to use the expression in the second half of 2 as it is, you'll get a
grammatically correct sentence like 4.

> 4 : 私は将来、 **自分の店を持ちたい** 。 or 私は将来、 **自分の店を持ちたい** です。

4 sounds much more natural to the native Japanese than 3.

If you want to use 夢 by all means in 4, it'll become like 5.

> 5 : 私は将来の夢として **自分の店を持ちたい** 。 or 私は将来の夢として **自分の店を持ちたい** です。

