"Goal is building/to build X"

Question

(1) Goal is building cheap SLA printer.
(2) Goal is to build cheap SLA printer.

Which is correct? And what rule do we need to use?

Answer 1

Neither. The correct sentence would be

The goal is to build a cheap SLA printer.

Edit: Why "to build" rather than "building"? Both are grammatically correct, but consider

My goal is becoming a doctor.

and

My goal is becoming unreachable.

Those sentences are very different. In the first sentence, the verb is "to be" ("is" is the third-person present indicative form of "to be") and links to the predicative complement, "becoming a doctor". In the second sentence, the verb is "become" ("is becoming" is the third-person present continuous form of "to become") and links to the predicative adjective "unreachable".

Those sentences are very different, but the difference is not apparent until the very last few words. To parse each sentence, the reader has to finish the sentence and then reason about its meaning. "What is 'becoming', my goal or me?" The sentences are somewhat burdensome to understand.

The sentence

My goal is to become a doctor.

is immediately understandable. As soon as the reader reaches "to", he can anticipate the sentence will tell him what the goal actually is. That makes using the infinitive form "to become" or "to build" stylistically preferable to using a gerund like "building" or "becoming".

It occurs to me that "My goal is becoming unreachable" might even be interpreted as a predicative complement, meaning "I wish to become a person who is unreachable." If that were the intended meaning, I could write "My goal is to become unreachable" -- but I don't know how to succinctly and unambiguously express my concern that my goal may not be as easy to reach as it used to be.