Question 1)
Information Management Teacher: Prof.
June 21, 2019
Time available 2:00 hours
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1. Illustrate the two phase commit protocol for the management of distributed commit.
2. Discuss the possible failures that the protocol could need to face and how they are addressed.
3. 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 =4)R(X =3)
P2: W(X = 1) R(X = 3) R(X = 4)
P3: R(X =1)R(X =4)W(X =3)
P4: W (X = 2) 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. What is a bitmap index? Clearly explain its advantages and disadvantages.
2. Considering the attached table, build the bitmap index for attribute PRODUCT and the bitmap index for attribute CITY.
Write the condition operating on bitmap indexes to filter sales for products P1 and P4 sold in Milan.
Question 3)
1. Fill the attached table illustrating the concepts of support, confidence, and lift in frequent itmeset mining.
2. Considering the table attached and assuming min sup=0.75 and min conf=0.8, identify all the frequent itemsets and
strong rules using Apriori algorithm.
Question 4)
Assume a distributed database for a franchising, where each shop keep tracks, for each product, of the quantity sold every day
, ShopId, ProductId, Date, Quantity). in a relation having schema SELL(Id
How would you use a MapReduce framework to identify, for each product, the shop and the data where the maximum quantity of the product have been sold? How would you define the map and the reduce functions?
Question 5) only for students who did not attend database course with Prof. Samarati
1. Illustrate the adoption of timestamps for concurrency control, clearly describing the rules according to which operations are accepted or discarded by a scheduler adopting either single-version or multi-version timestamp control.
2. AssumingamultiversionconcurrencycontrolbasedontimestampsandobjectxhavingtimestampRTM(x)=3andWTM(x)=1, respectively.
Fill the attached table indicating, for each operation in the table:
(a) if the operation is accepted or refused (b) the version of the object used
(c) the new values for RTM(x) and WTM(x) (d) the transaction eventually killed
Matr: Question
Surname, Name:
Final Mark:
Information Management – June 21, 2019
Matr: Surname, Name: Question 2.2
1 2 3 4 5 6 7 8
Rome Florence
Matr: Surname, Name: Question 3.1
Support(A → B)
Confidence(A → B)
Lift(A → B)
Matr: Surname, Name: Question 3.2 TID Items
1 ABCD 2 ACD
Matr: Surname, Name: Question 5.2
Killed transaction
read(x, 5)
write(x, 7)
write(x, 15)
read(x, 10)
read(x, 8)
write(x, 9)
write(x, 12)
read(x, 13)
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