The is a DBMS questions for Reading E-R Detail and answering the attached question.

Attached is the questions

below is what the professor responded to my answers 

(a) Okay.
(b) Okay.

(c) "removing the letter O" is not a correct statement.  It is not possible to remove a single lettered symbol.
    How would the company users describe the business situation in which an apartment would be removed from the database?  WHat in the model enforces that business situation?

(d) Your 1 and 3 are the same thing.  "Rental Contract Id" accepted as one good potential identifier.
    Your 2 cannot be a candidate key because of symbol I.
    You still need to come up with 2 more good potential identifiers.

(e) Please rewrite this as a complete answer to the question as it was asked.  Your answer might be okay, but it is difficult to tell as it is written.

(f) Okay, But better to say for 2: at least one Renter.

(g) You seem to be saying that an M:N used-by relationship would be acceptable.  It is NOT.  Why not?

(h) The situation will NOT involve redundancy.  No, the rented-by reln and the owned-by reln are completely independent and will not be conflicting.
    To answer this question, review the BUSINESS PURPOSE of the items involved.

(i) Your references to symbols I, J, K, L are wrong.  Those symbols are not involved in answering the question asked.  Please review the question carefully.

(j) Your answer is wrong.  You seem to be inventing things that the E-R model does not say, such as "in a real world only 1 individual can rent an apartment".

below here are my answers 

a) A New furniture can be recorded as soon as it is purchased because the Rental Contract
includes Furniture. Here the furniture is a part of Rental contract, so it will be recorded for theagreement purpose. F, S
b) Q, R, S, T is considered redundant. I will change the model by eliminating Q, R, S, T. userswon’t lose any information because Furniture is considered part of the contract and willobviously be the building if rented as a choice.
c) Under the condition of removing the letter O because if O is present then an apartment hasto be part of one or many buildings.
d) Two possible candidate ID are      1. Rental Contract Id       2. Apartment Id       3. Rental Ide) Yes, because a renter can have multiple Rental contract and an apartment must be rented by
many or one renter referring to C.
f) As the model is presented herewhat information must always be available for any rental contract in the database? (3 things)
  The Three things should be      1. Rental Contract Id      2. Renters Id      3. Apartment ID

g) A "used-by" relationship between Renter and Furniture will have an N: N relationshipOne Renter may have used many furniture and One Furniture may have been used by many
Renters.

h) If the owner of the building rents or leases an apartment in that building it will create
redundancy in the database because data will be stored unnecessarily at different places.Creating conflicting U, V, W, X with A, B, C, D

i) Since a rental contract is related to one and only one Apartment referring to K, L
Therefore, 4 students sharing an apartment will have to sign only 4 rental contract referring toI, J to indicate many contracts to apartment.

j) The feature that will never be used will be the Owner. They physical limitation will be that abuilding will always have an owner and there is nothing a renter can do about it.

Assignment C: Reading E-R Detail Together-While-Still Apartments Inc. (TWSA) manages the rental of furnished apartments and lofts using a database
whose Logical Data Model is shown here. Answer the questions below based this model only (i.e. "Discover, Don't Invent")
A yes/no answer is not sufficient. You must cite what specific part of the data model provides the answer.
The connectivity symbols are labeled with letters to make it easy to give short, specific, complete answers.
A letter (such as C or R) is sufficient to identify a minimum or maximum symbol in your answer.
Do not “over-answer” – if H alone is the right answer, do not say “G and H” or “E,F,G,H” (both wrong). A
Renter B C Rental
Contract G
H I J Furniture Apartment
K L
M
N
O
P in-use-at
Q R S part-of E
F rental-of includes rented-by D owned-by Building
T Owner
U V W X (a) Can new furniture be recorded as soon as it is purchased? How do you know? (b) What part of the model is redundant?
How would you change the model to eliminate the redundancy? Why won't users lose information if you make
this change? (c) Under what conditions will an apartment be deleted from the database? How do you know? (d) Suggest 3 good potential identifiers (candidate keys) for the Rental Contract entity.
(3 different alternatives, not one concatenation.) (e) Can TWSA use this database to track prospective new renters or former renters who might rent from them again?
How do you know? (f) As the model is presented here,
what information must always be available for any rental contract in the database? (3 things) (g) The office manager has suggested adding a “used-by” relationship between Furniture and the Renter.
What is your reply to this suggestion? Why? (h) What happens if the person who is the owner of a building rents (leases for his or her own use) an apartment in
that building?
Explain the effect on the database. (i) If 4 college students share a 2-bedroom apartment, how many rental contract instances will the roommates have to
sign? (j) One feature of this model will never be used because it exceeds a physical limitation of the
real world. Identify the item and describe the physical limit.

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