"That restaurant has already closed."
Yes either は or が is necessary to mark the subject. は is much more natural when used with もう because it marks the subject as a topic too.
If you are speaking you can often drop particles, but for correct written japanese you should include the は
No. This is the difference between "The restaurant is closed" vs "The restaurant has closed". The verb we are referring to is 閉まる which is an intransitive verb for "to close."
しまっています (is closed) refers to the continuous state of being closed, meaning that the restaurant is still undergoing the action of "closing" しまりました (has closed) refers to the past-tense immediate action of "closing", meaning that the restaurant finished starting the action of "closing"
If you say, "The shop closes at 10 P.M." and if the store closes at 10 P.M., then you could say "The shop has closed" when referring to when the shop started closing at the time 10 P.M. However, when you say "The shop is closed", you don't refer to when the shop performed the action of closing (at 10 P.M. in this example) but rather the continuous state that the shop is closed.
I think I only get a part of what you said. In your example, at 11pm, what is the difference between "The restaurant is already closed" and "The restaurant has already closed?"
What I read is only a nuance that "has closed" emphasizes that an action has been done and "is closed" emphasizes the continuous state of the subject. But when you want to say "I cannot go into the shop today" you don't quite care whether it "is closed" or "has closed."
I think this is also the case for the Japanese version 閉まりました(has closed) vs 閉まっています(is closed). From a day-to-day point of view the meanings should be close enough that they can be used interchangeably.
(Sorry for long answer, I'm trying to explain as much as I could; you could jump to different parts if you'd like)
I can understand why these may confuse you. Here we see the difference between present progressive behavior (Japanese form) vs present perfect behavior. In some cases (but not all), the two forms may be frequently interpreted as the same thing. Present progressive describes continuous activity (I am eating). Present perfect describes a past occurrence that led up to its current state (I have eaten). I'm no school teacher, but I do understand the difference very well, and I hope I am able to convey my thoughts to you.
In the example I used, "I am eating" describes the continuous action of someone eating at this moment in time. In the latter, "I have eaten" basically says that at some point in the past, the speaker already accomplished the task of eating AND that eating has affected the speaker's state.
Contrast this with the past simply tense "I ate" which just says that the speaker committed the simple action of eating at some point in the past (regardless of whether it affected the speaker's state). It is nonsensical to say "I have eaten breakfast yesterday" because, odds are, eating breakfast the day prior is not gonna have much of an effect on you, especially when you had eaten so many meals in between. Instead, you could say "I ate breakfast yesterday" (to simply describe the action - past simple) or "I had eaten breakfast yesterday" (to describe a point in the past where you already accomplished the task and had a change of state - past perfect). If this is part that bothers you, please read of on the differences between present progressive, present perfect, past simple, past progressive, and past perfect.
So if you understood what I said above, then "The store is closed" describe a continuous state of the store being closed, and so in the Japanese sense, you use the present progressive. However, in the example "The store has closed", you describe how the store accomplished the task of closing (whenever its closing time was), and that it had an effect on its current state (it is now closed). Compare that with "The store closed" (where the store committed the simple task of "closing" whenever closing time was) and "The store had closed" (where, at some point in the past, the speaker acknowledged that the store closed at closing time and that it affected the speaker at whatever time in the past they said that... but says nothing about its present state).
These may sound the same to you (and many people), but they are grammatically different. To give you an example where the distinction is more clear:
"The amusement park closed last year as a result of the hurricane." (past simple - says nothing about the present)
"I can't believe the amusement park is still closed!" (present progressive - only remarks its continuous present state but says nothing about the past)
"Ever since the hurricane last year, the amusement park has closed." (present perfect - remarks a past event that has had an effect on the present)
Also in your example, "I cannot go into the shop today" says nothing about the shop itself. In your example, the focus is on the speaker's action. Note that the verb of that sentence is "to go" and only describes the speaker. Maybe the speaker can't go into the shop because he has a fever or has other commitments.
(Sorry for writing up yet another long reply on top of a long one)
Thank you for your detailed explanation. I believe I get a clearer picture on the different tenses affecting how the speaker conveys the states and actions. However I think Japanese ～ている and ～た do not have a distinction that is as clear as the English counterparts.
This is clearer if we look at subordinate clauses
- 映画が始まっている (The movie is started)
- 始まっている映画はそれだ (Do not say that)
- 始まった映画はそれだ (That is the movie that is started)
The rule is to replace ている with た in subordinate clause if the verb is a stateful one.
Therefore I don't feel that 始まった and 始まっている has the clear distinction as in English (is started/has started) and both are grammatically correct - 映画がもう始まった and 映画がもう始まっている. Though I agree that they have subtle differences as in the English
So what bothers me is, whether we need to translate a sentence with the same grammatical structure, or we just need to convey a roughly same idea that people accept it as the "same."
I know that it is a philosophical question, so probably worth making a whole discussion thread on this.
But just taking an example in Duolingo: おはしを2本ください - Duolingo accepts "Can I get two chopsticks?" and "Please give me two chopsticks." Now two sentences are grammatically different, so why Duolingo accepts both? Isn't the sentence in Japanese a command, where "Can I get" is a question? Why not only accept "Please give me" as the correct answer?
I believe there is not a clear cut on whether a translation is "correct" or not. It is the question "how close a translation is so that we call it as "correct." So if we are saying "Can I get X" is a correct translation of ～ください, then "閉まっています” should also be a correct translation of "has closed" under a similar measurement.
I don't think I could properly answer that inquiry since I am not a native Japanese speaker. It may be the case that the subtle difference does actually exist in Japanese. I'm sure a lot of English speakers would believe that the past simple and present perfect (and many other tenses) are interchangeably equivalent in English even though they are grammatically not the same. This may also be the case for ～ている and ～た with Japanese speakers. I believe it is because of the frequency between the ～ている and ～た.
I am too much of a beginner to fully understand the grammatical (and social) usages of these rules in Japanese. I will keep all of this in mind and will research this if I become fluent.
Could you please change the English sentence to "That restaurant closed already."?