[SOLVED] CS代考 Question 1)

Question 1)
Information Management
Prof., Prof.
July 12, 2021

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Time available 2:00 hours (1:30 hours for students who do not answer to Q5)
1. Describethedifferencebetweendatacentricandclientcentricconsistency,clearlyillustratingwheneachofthemshould be used.
2. Consider the following schedule of operations performed by four processes over one variable (initially set to zero): P1: R(X =2)R(X =1)R(X =3)R(X =4)
P2: R(X =2)W(X =3)R(X =4)
P3: R(X =1)W(X =2)R(X =4)
P4: W (X = 1) R(X = 3) W (X = 4)
(a) Is the schedule sequential consistent?
If sequential consistency is satisfied, illustrate an equivalent sequence.
Otherwise, indicate the minimum number of operations (and which one) that should be removed to guarantee sequential consistency.
(b) Is the schedule causal consistent?
List all the causal dependencies in the schedule.
If the schedule it not causal consistent, indicate the operation(s) that should be removed to guarantee causal consistency.
Question 2)
1. Illustrate the concept of fact, dimension, and measure, providing an example.
2. Illustrate the Dimensional Fact Model (DMF) for the conceptual modeling of data warehouses. Provide an example of a
3. Compute the answer that would be computed by a relational system for the query in the attached page, operating on the table in the attached page.
Question 3)
1. Describe and discuss the classification and the clustering problems.
2. Illustrate the differences and similarities between these two problems.
3. Considering the table attached, build a decision tree using the information gain measure to choose the split attribute. For the exercise, stop at the first split and simply report the formulas to be computed for the choice.
Question 4)
Illustrate the main differences between a traditional relational database and a NoSQL database.

Question 5) only for students who did not attend database course with Prof. Samarati
1. Illustrate the fail-stop model for failure management.
2. Given the following log:
DUMP, B(T1), B(T2), I(T1,O1,A1), U(T2,O2,B2,A2), B(T3), D(T1,O3,B3), C(T1), B(T4), I(T3,O4,A4), I(T4,O5,A5), A(T4), CK(…), D(T2,O6A6), B(T5), I(T5,O7,A7), C(T3), U(T5,O8,B8,A8), B(T6), D(T6,O9,B9), A(T5), B(T7), U(T6,O10,B10,A10), C(T2) GUASTO
(a) write, for each checkpoint record, active transactions;
(b) illustrate in the details the steps of a warm restart to recover from failure.
RULES FOR THE EXAM
• Cover page: write only name, surname, matriculation number, if you did the exam with prof. Samarati
• White paper: write on each piece of paper name, surname, and matr. number (top left), number of the question (top right) • Use a different piece of paper for each question, for those questions that you decide to skip, draw a line
• Write only on one side of the paper.
• Do not write close to the margins: exams will be scanned for correction
• At the end of the time or upon request, deliver your exam (the exams delivered with delay will not be accepted) • Please, order the pieces of paper you are delivering for the exam as follows:
– cover page
– answers (in increasing order of question)

Matr: Question
Surname, Name:
DB with prof. Samarati?: (Y) (N)
Final Mark:
Information Management – July 12, 2021

Matr: product
t-shirt blue S 1000 t-shirt blue M 1100 t-shirt pink S 1000 t-shirt orange S 1200 skirt blue S 500 skirt blue M 560 skirt yellow S 600 skirt orange S 620 pull red S 600
Question 2.3
select product, color, size, sum(qty)
group by grouping sets ((product, color), (color, size))
Surname, Name: qty

1 low young 2low high 3low high
4 medium young 5 medium young 6 medium middle 7 medium high
8 high middle 9 high middle 10 high high
Surname, Name: class
y y y n y y n n n y
Question 3.3

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