Time available 2:00 hours (1:30 hours for students who do not answer to question 5)
1. Describe the differences between Lamport clocks and Vector clocks.
2. Consideringtheattachedschema,indicatethetimestampassociatedwitheachoperationofeachprocess.Fortheexercise, 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.
To answer the question, indicate in the order the values of the vector clock associated with each operation for each process:
P1 :vc1,vc2,… P2 :vc1,vc2,… P3 :vc1,vc2,…
3. Is there any process which does not know anything about another one? Which ones?
1. Describe OLTP and OLAP systems and clearly illustrate the differences between them.
2. Compute the answer that would be computed by a relational system for the query below, operating on the table on the
product flavor month quantity
cake chocolate jul 15 cake vanilla jul 5 cake vanilla aug 10
vanilla aug 25 strawberry aug 10
10 select product, flavor, sum(quantity) 20 from T
5 where flavor=”chocolate” or flavor=”strawberry” 20 group by cube (product, flavor)
1. Describe the relationship between the association rule mining and the frequent itemset mining problems.
2. Compute support and confidence of the association rules that can be obtained from the itemsets in the list below (the itemsets not in the list have frequency equal to 0).
Assume that the overall number of transactions is 40.
For the exercise, consider a minimum threshold for support min sup=0.50.
To answer the question, draw a table with columns
Itemset Frequency Itemset Frequency
A 40 B 20 C 30
AB 20 AC 30 BC 10
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 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.