Describe the OSI (Open Systems Interconnections) reference model and discuss examples of the networking functions normally associated with each component. [14 marks] (b) What do we mean by layer violation? Discuss some of the reasons that might lead a pragmatic protocol implementer to engage in layer violation and illustrate with an example. [6 marks] 4 Distributed Systems (a) You have been asked to design an event composition and aggregation service to operate above publish/subscribe middleware to be deployed in various environmental monitoring scenarios. Your service is to advertise and publish high-level events of interest to applications. It may subscribe to any published events in the domain of deployment. Your service may itself be distributed. Identify a list of technical design issues you would raise with your client prior to specifying the service in detail. [12 marks] (b) By means of a diagram illustrate the use of vector clocks to implement the delivery in causal order of multicast messages among members of a closed, unstructured process group. Include an explanation of the message delivery algorithm.

Some banks issue their Automatic Teller Machine (ATM) card customers with a randomly selected personal indentification number (PIN). Others issue their customers with an initial PIN only, and let the customers choose their own PIN the first time they use the card in an ATM. Describe the advantages and disadvantages of these approaches. [5 marks] Again, some banks compute the customer PIN by encrypting the account number using DES and a key known only to their central systems and ATMs, taking the first four hex digits of the result, replacing the digits A, . . . , F with 0, . . . , 5 respectively, and finally, if the first digit of the result is 0, replacing it with a 1. What is the probability that a criminal can get the PIN right given three guesses? [5 marks] Yet other banks have used DES, and a key known only to their central systems and ATMs, to encrypt the PIN (whether randomly generated or customer selected); they then write the result on the magnetic strip on the customer's card, so that the ATM can verify it without reference to the central system. Describe the disadvantages of this arrangement. [5 marks] In order to prevent attacks based on manipulating magnetic strips, banks in some countries have moved to using smart cards. What effect would you expect such a move to have on the incidence of card-based fraud?

A company has just completed the heuristic evaluation of a digital music player, and identified the problem areas provided in the list below. Indicate which usability principle or principles each problem violates for five of the following problems. [Note: it is possible that each problem violates more than one usability principle, and that the same principle is violated multiple times for different problems.] P1. Inconsistencies between menus and buttons. P2. Some language does not correspond with user terminology. P3. There are buttons that the user may not realize are buttons. P4. Not all buttons have tooltips. P5. There are inconsistencies with Windows operating system standards. P6. Undo commands basically unsupported. P7. Help content uses different terminology from application. P8. System does not always provide user with enough information about the task being performed. [5 marks] 7 (TURN OVER)

Write java program to read two integer and swap the values using third variable. a Java program to read a full names (first and last together) from a text file and print the name in the' last, first'

Explain how a parse-tree representation of a program may be converted into a stack-based intermediate language giving sketches of code to translate expressions, assignments and the if-then-else command; you should also explain how occurrences of a variable in an expression or assignment are translated. The program may be assumed to conform to the following syntax: E -> n | x | E + E | f(E,E) D -> let f(x,x) = {Dseq; Cseq; E} | let x = E C -> x := E; | if E then C else C Cseq -> C | C Cseq Dseq -> D | D Dseq with start symbol Dseq. Here n corresponds to integer constants, x corresponds to identifiers used as variable names and f corresponds to identifiers used as function names (you may assume these are disjoint). The function declaration construct has the effect of defining a function which, when called, makes declarations, performs commands and then returns the result of its expression; note that therefore functions may be defined within functions, but the above restriction on identifiers means that they cannot be returned as results. [20 marks] 8 Prolog for Artificial Intelligence Write Prolog programs that define the following predicates. Your programs should ensure that backtracking does not produce spurious alternative solutions. (a) The nth element of a list: nth(X,N,L) instantiates X to the Nth element of list L. Assume that list elements are numbered increasing from 1. [4 marks] (b) The last element of a list: last(X,L) instantiates X to the last element of list L. [4 marks] (c) Remove an element from a list: remove(X,L,M) instantiates M to a list containing all the elements of list L except for every occurrence of term X. [6 marks] (d) Substitute one element for another: subst(L,X,Y,M) instantiates M to a list containing all the elements of list L except that every occurrence of term X in L is replaced by term Y in M. [6 marks] 6 CST.98.12.7 9 Databases The relational model of data was introduced in the early 1970s in a sequence of papers by E.F. Codd. This model proposes a tabular view of data, with a simple Data Manipulation Language (DML) based on relational algebra or relational calculus. Briefly explain the essential features of the model and its DML. [6 marks] Later work by Codd and others addressed weaknesses in the expressive power of the relational model. For each of the following give an example to show how the weakness arises, and explain an approach proposed to resolve the difficulty: (a) computing the transitive closure [4 marks] (b) manipulating collections of records [4 marks] (c) handling entity specialisation [6 marks] In case (c) you should outline the proposals of either the Object-Oriented Database System Manifesto or the Third Generation Database System Manifesto. 10 Introduction to Functional Programming Write an ML function upto of type int -> int list such that upto n generates the list [1,2,3,...,n]. [7 marks] What is wrong with the following function to take the head of a list? fun wrong_headed [h,t] = h; What is the type of wrong_headed? [5 marks] Why is the following function to evaluate Fibonacci numbers inefficient? fun fib 0 = 1 | fib 1 = 1 | fib n = fib(n-1) + fib(n-2); Write a similar but more efficient version.

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4.9. Solve the following linear program using the simplex method. Explain each simplex pivot by showing a complete basis representation or simplex tableau for each extreme point visited. Compute the value of the objective function and decision variables at op- timality, and indicate which statement best describes the solution and why: Minimize Z- 7x - 5x X 24 10x + 3x 30 x + 2x = 10 X1, X = 0 Subject to: 2x (a) this linear program has a unique optimal solution (b) this linear program has alternate optima (c) this linear program is infeasible (d) this linear program is unbounded Problem 2 [250] Please solve Problem 4.9 in the textbook following the guidelines/instructions below: (a) [50] Provide the graphical solution. (Use the provided graph sheet or other graphing sheet - but be sure to implement a reasonable scale). Identify the feasible region and the optimal solution. Plot the objective function as a double dashed line (======) through the optimal point. Clearly identify the feasible region, the optimal point (x1, x2") and the Z" value. (b) [20] Augment the constraint set with slack/surplus variables as necessary. Use X3, X4, etc, as the slack/surplu: variable for constraint (i=1,2,3, etc), if that constraint needs one. Write out the full (augmented) linear program. (c) [100] Solve the LP using the Simplex (Dictionary) method. Always choose the variable that results in the larges improvement of the objective function, Z for each unit increase whenever there are more than 1 variable tha could be made Basic. Provide the simplified Dictionary at each iteration. State if the Dictionary is Phase I or II. If you need to add an artificial variable in Phase I, use Xo. (d) [20] Clearly state why you believe the final Dictionary is the optimal Dictionary. GIVE reasons. (e) [30] Characterize the optimal solution of 2(c) as one of the following: (i) Unique Optimal; (ii) Alternate Optima; (iii) Infeasible; (iv) Unbounded You must state the REASON for your characterization. No reason, no credit. (f) [30] On the graph of Problem 2[a], show the progression from the initial Phase I Dictionary to the optimal solution. 4.9. Solve the following linear program using the simplex method. Explain each simplex pivot by showing a complete basis representation or simplex tableau for each extreme point visited. Compute the value of the objective function and decision variables at op- timality, and indicate which statement best describes the solution and why: Minimize Z- 7x - 5x X 24 10x + 3x 30 x + 2x = 10 X1, X = 0 Subject to: 2x (a) this linear program has a unique optimal solution (b) this linear program has alternate optima (c) this linear program is infeasible (d) this linear program is unbounded Problem 2 [250] Please solve Problem 4.9 in the textbook following the guidelines/instructions below: (a) [50] Provide the graphical solution. (Use the provided graph sheet or other graphing sheet - but be sure to implement a reasonable scale). Identify the feasible region and the optimal solution. Plot the objective function as a double dashed line (======) through the optimal point. Clearly identify the feasible region, the optimal point (x1, x2") and the Z" value. (b) [20] Augment the constraint set with slack/surplus variables as necessary. Use X3, X4, etc, as the slack/surplu: variable for constraint (i=1,2,3, etc), if that constraint needs one. Write out the full (augmented) linear program. (c) [100] Solve the LP using the Simplex (Dictionary) method. Always choose the variable that results in the larges improvement of the objective function, Z for each unit increase whenever there are more than 1 variable tha could be made Basic. Provide the simplified Dictionary at each iteration. State if the Dictionary is Phase I or II. If you need to add an artificial variable in Phase I, use Xo. (d) [20] Clearly state why you believe the final Dictionary is the optimal Dictionary. GIVE reasons. (e) [30] Characterize the optimal solution of 2(c) as one of the following: (i) Unique Optimal; (ii) Alternate Optima; (iii) Infeasible; (iv) Unbounded You must state the REASON for your characterization. No reason, no credit. (f) [30] On the graph of Problem 2[a], show the progression from the initial Phase I Dictionary to the optimal solution.

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Conversation with Gemini expandmoreedit Describe the OSI Open Systems Interconnections reference model and discuss examples of the networking functions normally associated with each component 14 marks ... View the full answer