EXAMINATIONS 2013 MID-YEAR SWEN 432 ADVANCED DATABASE DESIGN AND IMPLEMENTATION

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1 EXAMINATIONS 2013 MID-YEAR ADVANCED DATABASE DESIGN AND IMPLEMENTATION Time Allowed: 3 Hours (180 minutes) Instructions: Attempt all questions. There are 180 possible marks on the exam. Make sure your answers are clear and to the point. Non-programmable calculators without full alphabetic keys are permitted. Non-electronic foreign language dictionaries are permitted. Refer to the Appendix. No other reference material is allowed. Answer in the appropriate heavily outlined boxes or follow the instructions given in the questions. Question Topic Marks 1. SQL:1999 WINDOW [15 marks] 2. Query Rewriting [45 marks] 3. XML, Constraints, and Normal Form [80 marks] 5 XQuery [40 marks] Note: Marks are shown for each question as a whole and also for their parts.

2 Question 1 SQL:1999 WINDOW [15 marks] SQL:1999 standard introduced recently an extension to the SELECT statement to enable computing query results containing overlapping ordered groups of rows with aggregates appended to each row. This extension is called WINDOW. The WINDOW syntax is given in Appendix. Consider the Assignments table on the facing page. a) [8 marks] Define a SQL:1999 statement that calculates the cumulative sum of assignment marks for each student and for each of his/her courses. The semantics of the cumulative sum should be the total number of student s marks after assignment x of the course y, where x = 1, 2,.., and y = COMP426, NWEN404, SWEN432,... The output should be sorted according to the ascending values of the (StudentId, CourseID, AssignmentNo) triples. 2

3 b) [7 marks] Use the empty table below to show the result of your query. Assignments StudentId CourseId AssignmentNo Marks 007 SWEN SWEN SWEN COMP SWEN COMP SWEN SWEN COMP COMP SWEN NWEN NWEN NWEN

4 Question 2 Query Rewriting [45 marks] a) [15 marks] In lectures, we considered the following three query rewrite methods of a contemporary ROLAP engine: The full text match, The partial text match, and The general query rewrite method. Give a brief outline of all three query rewrite methods. Include a brief outline of the four rewrite checks employed by the general query rewrite method. 4

5 b) [30 marks] Consider the following star schema: {Sales ({TimeId, ProdId, ShopId, Amnt }, { TimeId + ProdId + ShopId }), Time ({TimeId, Day, Week, MonthId, Month_Name, Year }, {TimeId}), Product ({ProdId, Prod_Name, TypeId, Type_Name, Industry }, {ProdId }), Location ({ShopId, CityId, City_Name, Country }, {ShopId })} Suppose attribute hierarchies are defined using the following sets of functional dependencies: Product hierarchy: ProdId Prod_Name, ProdId TypeId, TypeId Type_Name, TypeId Industry. Time hierarchy: TimeId Day, TimeId Week, TimeId MonthId, MonthId Month_Name, MonthId Year. Location hierarchy: ShopId CityId, CityId City_Name, CityId Country. Suppose the only materialized view defined is: CREATE MATERIALIZED VIEW avg_prod_city_month AS SELECT ProdId, Prod_Name, CityId, City_Name, MonthId, Month_Name, COUNT(*), AVG(Amnt) FROM Sales NATURAL JOIN Time NATURAL JOIN Location GROUP BY ProdId, Prod_Name, CityId, City_Name, MonthId, Month_Name; Note: The star schema, attribute hierarchies, and the materialized view above are also given in the Appendix. Consider the following queries issued against the star schema above and answer whether they can be evaluated using the materialized view avg_prod_city_month. If you think a query can not be answered using the view avg_prod_city_month, justify your conclusion. If you think a query can be evaluated using the materialized view: State the simplest query rewrite method that can be used and show how. Compare the complexity of your rewritten query with the original one and draw a conclusion whether a good OLAP processor would apply the rewriting. Use the number of JOIN, of DISTINCT, and of GROUP BY clauses to express the query complexity. Assume the application of the full text match is the simplest query rewrite method and the general query rewrite is the most complex. 5

6 i) [6 marks] The query Q1: Q1: SELECT ProdId, Prod_Name, CityId, City_Name, MonthId, Month_Name, COUNT(*), AVG(Amnt) FROM Sales NATURAL JOIN Time NATURAL JOIN Location GROUP BY ProdId, Prod_Name, CityId, City_Name, MonthId, Month_Name; 6

7 ii) [7 marks] The query Q2: Q2: SELECT City_Name, Month_Name, AVG(Amnt) FROM Sales NATURAL JOIN Time NATURAL JOIN Location GROUP BY City_Name, Month_Name; 7

8 iii) [10 marks] The query Q3: Q3: SELECT Industry, Country, Year, SUM(Amnt) AS Total FROM Sales NATURAL JOIN Product NATURAL JOIN Location NATURAL JOIN Time GROUP BY Industry, Country, Year; 8

9 iv) [7 marks] The query Q4: Q4: SELECT Industry, City_Name, Day, SUM(Amnt) AS Total FROM Sales NATURAL JOIN Product NATURAL JOIN Location NATURAL JOIN Time GROUP BY Industry, City_Name, Day; 9

10 SPARE PAGE FOR EXTRA S Cross out the rough working that you do not want marked. Specify the question number for work you do want marked. 10

11 SPARE PAGE FOR EXTRA S Cross out the rough working that you do not want marked. Specify the question number for work you do want marked. 11

12 Question 4. XML, Constraints, and Normal Form [80 marks] There are an XML Schema CD_Company.xsd, and an XML document CD_Company.xml given in the Appendix. The document CD_Company.xml is an instance of CD_Company.xsd. Use them to answer the question. The XML schema describes the database of a company that produces music albums on CDs. The database contains data about musicians, instruments and albums. A musician may be a singer, an instrument player, or both. An instrument player may play several instruments. Music albums contain songs performed by musicians. The CD company runs business under the following rules: 1. Each musician has a compulsory unique name. 2. Each instrument has a compulsory unique name. 3. Each album has a compulsory unique title. 4. Each song on an album has a unique ordinal number and a unique name. 5. Different albums may contain the same song even with the same ordinal number and name. 6. Musicians having their data in the database are registered and eligible to perform songs on albums. 7. A musician as a performer can sing a song if she/he has been registered as a singer. 8. A musician as a performer can play an instrument if she/he has been registered as a player of that instrument. 9. Musicians and instruments are referenced by their names on album labels. 10. A musician can have several roles when performing a song of an album (i.e. singing, playing various instruments). None of the rules above has been defined as constraints in the XML Schema, but the XML CD_Company.xml document obeys to all of them. 12

13 a) [9 marks] Map the CD_Company.xsd schema into a DTD schema with a minimally possible loss of structuring information and constraints. b) [8 marks] There is an XML document CD_Company_WRONG.xml given in the Appendix. The document validates against CD_Company.xsd, although it violates rules number 1, 4, 6, and 8 above. Find all four errors. In your answer, quote document line numbers that diagnose the rule violation and the rule violated. 13

14 c) [12 marks] In the next four questions, you will consider whether it is possible to use attributes of the type ID/IDREF to implement constraints that will enforce the rules number 1, 4, 6, and 8 above. The ID/IDREF constraints you define should not imply the need to change CD_Company.xml. If you think it is possible, show the corresponding fragment of CD_Company.dtd after your change. If you think it is not possible, justify your claim. i) [2 marks] Rule number 1: Each musician has a compulsory unique name. ii) [4 marks] Rule number 4: Each song on an album has a unique ordinal number and a unique name. iii) [2 marks] Rule number 6: Musicians having their data in the database are registered and eligible to perform songs on albums. 14

15 iv) [4 marks] Rule number 8: A musician as a performer can play an instrument if she/he has been registered as a player of that instrument. d) [18 marks] In the next four questions you will use the XML Schema identity constraints of the type key, keyref, unique to implement constraint(s) that will enforce rules number 1, 4, 6, and 8 above. If you think a rule can not be declared using identity constraints, justify your claim. In your answer, clearly designate the context node of the constraint. Note: The syntax of the identity constraints is given in the Appendix. i) [4 marks] Rule number 1: Each musician has a compulsory unique name. 15

16 ii) [4 marks] Rule number 4: Each song on an album has a unique ordinal number and a unique name. iii) [4 marks] Rule number 6: Musicians having their data in the database are registered and eligible to perform songs on albums. 16

17 v) [6 marks] Rule number 8: A musician as a performer can play an instrument if she/he has been registered as a player of that instrument. e) [5 marks] How many maximal tree tuples of Arenas&Libkin are contained in the CD_Company.xml document tree? Justify your answer 17

18 f) [8 marks] Does the CD_Company.xml document satisfy the following functional dependency of Arenas&Libkin CD_Company.Album.Song.Performer.Sings Use node identifiers given in CD_Company.xml document to answer the question. g) [12 marks] Use notation of Arenas&Libkin to define (key defining) functional dependencies for rules 1, 2, 3, and 4. 18

19 h) [8 marks] Consider the CD_Company.dtd you have produced by answering question 4 a) and the CD_Company.xml document in the Appendix. Can you identify any anomalous functional dependency of Arenas&Libkin? Justify your answer. 19

20 i) [10 marks] Designate the set of functional dependencies you have defined by answering questions 4 e) and f) above by. Is (CD_Company.dtd, ) in the XML normal form of Arenas&Libkin? Justify your answer. If you think it is not, transform your CD_Company.dtd into CD_Company_XNF.dtd so that (CD_Company_XNF.dtd, ) is in the XML normal form of Arenas&Libkin. In your answer, you may show only commented changes you have made to CD_Company.dtd. 20

21 Question 5. XQuery [40 marks] Consider the Bank_Robbery.xml document given in the Appendix. Use XQuery to define the following queries against Bank_Robbery.xml: a) [5 marks] Retrieve Robber_Id, Nick_Name, and Years_In_Prison of all robbers who were in jail, sorted in decreasing order of the number of years spent in jail. The output of your query should adhere to the structure and constraints of the following DTD fragment: <!ELEMENT Robber (Nick_Name)> <!ELEMENT Nick_Name (#PCDATA)> <!ATTLIST Robber Robber_Id ID #REQUIRED Years_In_Prison CDATA #REQUIRED> 21

22 b) [5 marks] Retrieve robbers who have both Planning and Preaching skills. The output of your query should adhere to the structure and constraints of the following DTD fragment: <!ELEMENT Robber (Nick_Name)> <!ELEMENT Nick_Name (#PCDATA)> c) [8 marks] Retrieve name, city, and robbery date of all banks robbed by Al Capone. The output of your query should adhere to the structure and constraints of the following DTD fragment: <!ELEMENT Banks_Robbed_by_Al (Bank*)> <!ELEMENT Bank EMPTY> <!ATTLIST Bank name CDATA #REQUIRED city CDATA #REQUIRED robbery_date CDATA #REQUIRED> 22

23 d) [8 marks] Retrieve Robber_Id, Nick_Name, Age, and Skills of all robbers who are between 20 and 40 years old. The element Skills should contain all skills of a robber. <!ELEMENT <Skills_of_Middle_Aged_Robbers (Robber*)> <!ELEMENT Robber (Nick_Name, Skills)> <!ELEMENT Nick_Name (#PCDATA> <!ELEMENT Skills (#PCDATA> <!ATTLIST Robber Robber_Id ID #REQUIRED Age CDATA #IMPLIED> 23

24 e) [14 marks] Retrieve the nick name and the total earnings of those robbers who have earned more than average by robbing banks. The output of your query should adhere to the structure and constraints of the following DTD fragment: <!ELEMENT Earnings (Average, Robber*)> <!ELEMENT Average (#PCDATA)> <!ELEMENT Robber EMPTY> <!ATTLIST Robber name CDATA #REQUIRED> <!ATTLIST Robber total_earning CDATA #REQUIRED> 24

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26 SPARE PAGE FOR EXTRA S Cross out the rough working that you do not want marked. Specify the question number for work you do want marked. *********** 26 end