[SOLVED] 计算机代考 ALL 370 pants ALL ALL 330 ALL red ALL 170 ALL blue ALL 430 ALL

Question 1)
Information Management Teacher: Prof.
July 9, 2019
Time available 2:00 hours

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1. Illustrate the concept of happened before characterizing logical clocks.
2. Describe the differences between Lamport clocks and Vector clocks.
3. 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.
4. 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. Considering the attached relation T , write the three SQL queries operating on T that would generate the three relations reported 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)
Assume a distributed database for a company where each warehouse keeps track, for each product on storage, of the available
, ProductId, WarehouseId, Quantity). quantity in a relation having schema AVAILABILITY(Id
Assume that the company fixes a minimum overall threshold for re-ordering products.
How would you use a MapReduce framework to identify which product should be re-ordered?
Question 5) only for students who did not attend database course with Prof. Samarati
1. Illustrate the adoption of two phase locking for concurrency control, clearly describing the working of two and three states lock managers.
2. Given the following shedule:
w4(x) r1(y) r1(x) r4(t) r4(z) w3(y) w3(x) w4(z) w2(z) w1(t) w2(t)
Tell if it could have been generated by a scheduler based on base 2PL , considering a two states lock. Justify your answer illustrating the schedule evaluation step by step.

Matr: Question
Surname, Name:
Final Mark:
Information Management – July 9, 2019

Matr: Surname, Name: Question 1.4

Surname, Name:
Question 2.3
t-shirt red t-shirt blue t-shirt red t-shirt white pants blue pants blue pants white pants white
t-shirt red t-shirt blue pants blue pants white t-shirt ALL pants ALL ALL red ALL blue ALL white ALL ALL
Milan 100 Milan 150 Florence 70 Florence 50 Milan 200 Florence 80 Milan 20 Florence 30
100 150 200
t-shirt red Milan 100 t-shirt blue Milan 150 t-shirt red Florence 70 pants blue Milan 200 pants blue Florence 80 t-shirt red ALL 170 t-shirt blue ALL 150 pants blue ALL 280 t-shirt ALL ALL 320 pants ALL ALL 280 ALL ALL ALL 600
product quantity
t-shirt ALL ALL 370 pants ALL ALL 330 ALL red ALL 170 ALL blue ALL 430 ALL white ALL 50

Surname, Name: class
y y y n n y n n y y
Question 3.3
mar status
4single 1 5single 2 6 divorced 3 7 married 2 8 divorced 3 9single 3 10married 1
married 1 married 1 married 2

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