15 02 18ts

Page 1

DATA BASES 2 – FEBRUARY 15TH, 2018 – TIME: 2H 15M PROF. DANIELE M. BRAGA, PROF. STEFANO PARABOSCHI A. Active Databases (9 p.) GENETICPROFILE (SubjectId, Sex, MaleParentId, FemaleParentId, Inherited, PercProp) The table describes genealogical info rmation, with focus on the representation of a single inherited property (real systems manage many properties ). The attribute PercProp represents (as a percentage) the degree of the property expressed by the subject. If Inherited is true , the value of PercProp is equal to the average between the values of PercProp expressed in the parents. Inherited is true only when both parents are present in the table. Write a set of triggers that manage the value of PercProp reacting to insertions of new subjects and to updates to the value of PercProp for subjects with Inherited equal to false. Discuss the termination of the proposed triggers. B. Concurrency Control (6 p.) In a hierarchy of resources P1(A,B,C), P2(D,E,F) page P1 contains resources A, B, C and page P2 contains D, E, and F. (1) Classify the following schedule. w1(A) r2(P2) w3(C) w2(E) r1(E) r2(C) r3(A) (2) List the sequence of lock requests submitted to the lock manager by transactions T1..T3, assuming that all transactions know in advance all the operations that they will perform, and that each transactions follows a 2PL -strict approach, showing the behavior and the final status of the system. (3) From a general perspective, discuss why the structure of schedules compatible with TS-mono concurrency control exhibits a limited risk of deadlock when executed in a 2PL-strict mode. C. XML (9 p.) <!ELEMENT DreamCars ( Car* )> <!ELEMENT Car ( PlateNumber, Model, Color, Year, Mileage, Rental* )> <!ELEMENT Rental ( Member, PickupDate, ReturnDate?, Purpose, Price )> <!ELEMENT…