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Data Bases 2 Prof. S. Paraboschi – January 19th, 2011 – Time: 2h15m A. (DB2_I) Concurrency control (6 points) Classify with respect to VSR, CSR and Multi-TS the following schedule S 0. Classify also schedule S 1, obtained from S0 moving the first operation to the last position. r1(X) w 0(X) w 1(X) w 3(X) r 2(X) B. (DB2_II) Distributed Databases (6 points) An environmental monitoring system in the Lombardy region consists of several aggregation nodes, each connected to a set of sensors. Sensors collect meas ures of the concentration of CO2, PM, and CO. Each measure is associated with a timestamp. Measures ar e transmitted from the sensors to the aggregation n odes, which aggregate them and send them to the central n odes every 5 minutes. There are 4 central nodes and there is the need to guarantee redundancy, keeping at least two copies of the data. Design the database and the corresponding distribut ion strategy. Express at the levels of fragmentatio n and language transparency the query that extracts the d ays when the concentration of PM measured on the aggregation nodes went at least once over 200, in Milan or in 50% of the locations in Lombardy. C. (DB2_III) XML (6 points) <!ELEMENT Libraries ( Library* )> <!ELEMENT Library ( Area, Address, Book+ )> <!ELEMENT Book ( Description? )> <!ATTLIST Book id ID #REQUIRED Genre CDATA #REQUIRED numPages CDATA #REQUIRED> The schema describes libraries in Milan. The elements left unspecified only contain PCDATA. Note that an area can be served by more than one library. 1) Extract in XQuery all the libraries with more than 100 books of genre “Computer Science” (2 p.) 2) Build a document that contains, for each area, the total number of books for each genre (4 p.) D. (DB2_IV) Active databases (6 points) A trigger system computes…