"Above the coffee shop there is a library."
When is it (un) necessary to add the possessive "de" behind a noun?
Just to make it easier to talk about things, I’ll label the words like this:
- If A is a noun, 的 is normally necessary. The only exceptions I can think of:
a) A is a personal pronoun and B denotes a close relationship with A: 我(的)妈妈、我(的)朋友、我(的)老师 b) A is a personal pronoun (almost always in plural) and B is an institution (in the wider sense) of which A is a part (typically: 他们(的)公司、你们(的)家、我们(的)单位 c) B denotes a spacial relation with respect to A: 咖啡馆(的)上面、学校(的)前边 (note that this only goes for 2-syllable B's. If B is just one syllable, it attaches directly and 的 cannot be used: 桌子上、门口前) d) after a verb, when A is a time duration and B is the object of the verb: 我游了一个小时(的)泳。他看了二十分种(的)书。
If A is a verb phrase or an adjective, you also usually need 的, except:
- if A is a "bare" adjective (without any adverbs and such): 好(的)书、熱(的)包子
So in this case 咖啡馆的上面 and 咖啡馆上面 should both be accepted.
It is usually necessary. As far as I know, the exceptions are: 1) The there is/there are sentence structure "A上面有B" meaning "There is B above A" specifically does not require it. You do not need to put "的“ between A and 上面。 (The same goes for any direction/preposition you fill in here.) So why did Duo include the 的 in this sentence? My guess is, for clarity, since the sentence has a lot of characters. We do a simlar thing in English with the pronoun "that" indicating a subordinate clause. We usually omit it in short sentences, but include it for clarity in long sentences. Compare: "She lives next to the house (that) I grew up in" versus "She lives next to the house that I moved into when I was 3, left for 7 years, then returned to at age 10." The first sentence sounds OK with or without "that," but the second sentence becomes more confusing without "that," even though the grammatical reasons to use "that" are the same for both sentences. 2) 的 is dropped for very close relationships, for example you say "我妈妈“ not "我的妈妈" and "他爸爸“ not”他的爸爸“. I was taught to drop 的 for all family members, but I have noticed that Duo sometimes retains 的 for more distant family members such as 阿姨. I think it is also sometimes OK to drop the 的 before “朋友” as in "我朋友“. Duo does this sometimes in short sentences.
Any positions, any part of a thing, any relationship between two things. Any time when you have "of the " in English.
The sentence咖啡馆的上面有图书馆。doesn't sound casual and a it unnatural to me.
Here's what I think it should be: 在咖啡店的上面有一个图书馆。
(I replaced "馆" with "店" because "馆" can refer to things other than shops and "店" only refers to shops/stores.)