CPS 432/562 Homework #5

1. (5+5=10 points) Exercise 18.6.1 (only parts b and c) on p. 963 from [DBCB]: Consider, for variety, an object-oriented database. The objects of class C are stored on two blocks, B₁ and B₂. Block B₁ contains objects O₁ and O₂, while block B₂ contains objects O₃, O₄, and O₅. Class extents, blocks, and objects form a hierarchy of lockable database elements. Give the sequence of lock requests and the response of a warning-protocol-based scheduler to the following sequences of requests. You may assume all requests occur just before they are needed, and all unlocks occur at the end of the transaction.
   
   
   1. r₁(O₅); w₂(O₅); r₂(O₃); w₁(O₄);
   2. r₁(O₁); r₁(O₃); r₂(O₁); w₂(O₄); w₂(O₅);
   
   
2. (10 points) Exercise 20.3.2 (only part c) on p. 1070 from [DBCB]: Consider the following relations:

   Computer(number, proc, speed, memory, hd)
   Monitors(number, screen, maxResX, maxResY)
   

   Understand that the attribute number of both relations to refer to the number of a complete system, some of whose attributes are found in one source and some in the other. Suppose that the adornments describing access to the Computers relation are buuuu, ubbff, and uuubb, while the adornments for Monitors are bfff and ubbb. For the following query, give 2-3 feasible plans (exclude any plans that are obviously more expensive than other plans on your list):
   
   
   Find all systems with a G4 processor running at 750 megahertz with 256 megabytes of memory, a 40 gigabyte disk, and a 17-inch monitor.
   
   
3. (15 points) Describe a data management or search problem which involves integrating information from multiple web sources. For example, planning a vacation may require culling information from online flight and hotel reservation systems, car rental websites, and tourist guides. Filling your taxes online is another popular example, especially around this time of year. Here we would require documents detailing our income and benefits from employer HR websites, end of year statements from our banks and investment companies, and online filing forms from federal and state websites. Indicate which web sources you will use and how they satisfy your information needs. Next discuss which approach to information integration (federation, mediation, or warehousing) you would take and why. Be specific. Include advantages and disadvantages, and tradeoffs. Describe how you will extract information from the sources to answer queries. For example, will you build wrappers? If so, how sensitive will they be to the underlying sources, how will they be implemented, and how will they adapt? How will your wrappers or interfaces expose the underlying data and capabilities of the sources to other components. For instance, will they use relational schemas, flat files, or information hierarchies? Are any indices necessary? Finally, give 3 specific queries that your solution approach would accommodate and for one of them provide a feasible query plan.
   
   
4. (15 points) Read one of the articles in the section on data warehouses in the December 2001 issue of IEEE Computer (if you are seeking access from a computer outside of the UD network, you made need to may need to authenticate yourself here) and write a 2 page (11pt Times font, single-spaced, 1" margins) analysis of it. Your analysis should contain about a page of text summarizing the article. Your summary should answer the following questions: What problem does the paper address? What solution approach was taken and why? What is the most central contribution to the database community made in the paper? In addition, your analysis should address the advantages and disadvantages of the solution, how it scales, and how it aligns with existing approaches. Since these articles are nearly 5 years old now, briefly discuss what new developments in the field of database systems have augmented/superseded this work. Lastly, identify and explain what new things you learned, beyond what we have covered class, by reading this article.
   
   
5. (10 points) Required only for CPS 562 students
   We studied the usefulness of an SIX mode for multiple-granularity locking. Explain why an exclusive and intension-shared (XIS) mode is of no use.