Exercise 18.2.1: Below are two transactions, described in terms of their effect on two database elements A and B, which we may assume are integers. Ti: READ(A, t); t:= t+ 2 ; WRITE(A ,t) ; READ(B, t); t:= t* 3 ; WRITE(B, t); T2: READ(B, s); s:=s*2; WRITE(B, s); READ(A, s); s:=s+3; WRITE(A. s); 896 CHAPTER 18. CONCURRENCY CONTROL We assume that, whatever consistency constraints there are on the database, these transactions preserve them in isolation. Note that A = B is not the consistency constraint. a) It turns out that both serial orders have the same effect on the database; that is, (Ti ,T2) and (T2,T i) are equivalent. Demonstrate this fact by showing the effect of the two transactions on an arbitrary initial database state. b) Give examples of a serializable schedule and a nonserializable schedule of the 12 actions above. c) How many serial schedules of the 12 actions are there?

Facial expressions and gestures are examples of messages.

The volume v and paper surface area a of a conical paper cup are given by where r is the radius of the base of the cone and h is the height of the cone. a. by eliminating h, obtain the expression for a as a function of r and v. b. create a user-de ned function that accepts r as the only argument and computes a for a given value of v. declare v to be global within the function. c. for v ! 10 in.3 , use the function with the fminbnd function to compute the value of r that minimizes the area a. what is the corresponding value of the height h? investigate the sensitivity of the solution by plotting v versus r. how much can r vary about its optimal value before the area increases 10 percent above its minimum value?

This question involves a class named textfile that represents a text file. public class textfile { private string filename; private string filename; private arraylist words; // constructors not shown // postcondition: returns the number of bytes in this file public int filesize() { } // precondition: 0 < = index < words.size() // postcondition: removes numwords words from the words arraylist beginning at // index. public void deletewords(int index, int numwords) { } // precondition: 0 < = index < = words.size() // postcondition: adds elements from newwords array to words arraylist beginning // at index. pub lic voidaddwords(int index, string[] newwords) { } // other methods not shown } complete the filesize() method. the filesize() is computed in bytes. in a text file, each character in each word counts as one byte. in addition, there is a space in between each word in the words arraylist, and each of those spaces also counts as one byte. for example, suppose the words arraylist stores the following words: { mary had a little lamb; its fleece was white as snow. } the filesize() method would compute 4 + 3 + 1 + 6 + 5 + 4 + 6 + 3 + 5 + 2 + 5 as the sum of the lengths of each string in the arraylist. the value returned would be this sum plus 10, because there would also be 10 spaces in between the 11 words. complete the filesize() method below: // postcondition: returns the number of bytes in this file public int filesize() { }