[SOLVED] CS代考 Question 1)

Question 1)
Information Management
Prof., Prof.
June 21, 2021

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Time available 2:00 hours (1:30 hours for students who do not answer to Q5)
1. Describe the concept of logical clock, illustrating its importance, advantages, and disadvantages in distributed scenarios.
2. Fill the attached schema indicating the timestamp associated with each operation of each process. For the exercise, assume to adopt Vector clocks and that all the timestamps are initialized to 0. Operations are denoted with a tick on the line of the corresponding process.
3. Is there any process which does not know anything about another one? Which ones?
Question 2)
1. Illustrate the multidimensional logical modeling of data warehouses.
2. Describe the star and snowflake schemas for data warehouses, illustrating their differences.
3. Compute the answer that would be computed by a relational system for the query below, operating on the table on the left.
Question 3)
1. Describe and discuss the association rule mining and the frequent itemset mining problems.
2. Illustrate the relationship between these two problems.
3. Illustrate the apriori property for the efficient identification of frequent itemsets.
4. Considering the table attached and assuming min sup=0.75, identify all the frequent itemsets using apriori algorithm.
Question 4)
Illustrate and discuss the CAP Theorem, and its practical implications in the context of NoSQL databases.
Question 5) only for students who did not attend database course with Prof. Samarati
1. IllustrateACIDproperties.
2. Given the following schedule
r3(z) w1(x) r4(y) w2(x) w2(y) w3(z) r3(y) r3(x) w3(y)
tell if it is VSR and/or CSR indicating (when existing) all the equivalent serial schedules.
RULES FOR THE EXAM
• Cover page: write only name, surname, and matriculation number
• 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
• 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
Question Position:
Surname, Name:
Final Mark:
Information Management – June 21, 2020

Matr: Surname, Name: Question 1.3

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
Surname, Name: qty
select product, color, size, sum(qty) from T
where color=”blue” or color=”orange” group by rollup (product, color, size)

Matr: Surname, Name: Question 3.4 TID Items
1 A,B,C,E 2 A,C,E
3 A,B,D,E 4 A,B,C,D

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