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Toronto CSC 340 - CSC 340 Midterm Test

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CSC340 Information Systems Analysis and Design page 1/8Faculty of Arts and ScienceUniversity of TorontoMidterm TestDepartment: Computer ScienceInstructor: Steve EasterbrookDate and Time: 9:10am, Friday November 5, 2004Conditions: Closed BookDuration: 50 minutesThis test counts for 20% of your final gradeName: _______________________________________________________(Please underline last name)Student Number:_______________________________________________Question Marks1 ______________/202 ______________/203 ______________/304 ______________/30Total___________/100CSC340 Information Systems Analysis and Design page 2/81. [Short Questions; 20 marks total](a) [Software Lifecycles – 5 marks] Name two alternatives to the waterfall model. Whatare the advantages and disadvantages of each model when used to plan a software developmentproject?Spiral model.Advantages: allows for iterative development, with prototyping and risk management builtin to the process. Disadvantages: Might be expensive (and slower) to do lots of iterations.Not clear what happens if there are unexpected changes in business priorities,Incremental development.Advantages: don’t need to understand all the requirements before developing the firstversion. Lessons from early versions feed into later versions. Disadvantages: hard to planfor versions beyond the first. Lessons from early versions might be learnt too late. Mightmislead customer if first version doesn’t match many of their requirements.[Notes: Other possible lifecycles models include: Incremental development, prototyping,V-model, agile development, XP, etc. Must have both advantages and disadvantages for twodifferent models to get full marks.](b) [Professional Ethics – 5 marks] Describe (in your own words) two differentguidelines that you might expect to find in a professional code of ethics for software engineers.In what way are these elements important in Requirements Engineering?Sample answer:1) “Software Engineers should always act consistently with the public interest.”2) “Software Engineers should ensure that their products and related modifications meetthe highest professional standards possible.”In requirements engineering, (1) suggests that the requirements engineer should take intoaccount the needs of the general public as a stakeholder in any systems analysis. Forexample, if a proposed system might cause harm to people, the environment, or mightdisadvantage certain groups in society, this should be described fully in the analysis. (2)suggests that requirements engineers should make sure they use industry standards, andadopt state-of-the-art methods and tools, wherever these are shown to be superior.[Notes: give credit for any other reasonable guidelines. Must give clear description of howboth the stated guidelines apply in RE to get full marks.]CSC340 Information Systems Analysis and Design page 3/8(c) [Systems Theory – 5 marks] In systems thinking, the principle of complementaritysuggests that different stakeholders are likely to tell you different things about a system theyobserve. Explain the principle, and state the circumstances to which it applies. Why is it hard toeliminate complementarity?Two descriptions of a system are said to be complementary if they overlap in somerespects, but neither can be entirely explained in terms of the other. The principle ofcomplementarity says that this is likely to occur whenever we have different stakeholdersgiving us partial views of a complex system.Complementarity disappears if the views are not partial, ie. if each stakeholder describeseverything that it is possible to observe about a system. However, this is hard to achievein practice with complex systems, because it is impossible for anyone to observe anddescribe the system fully. Each person’s view is filtered by their own interests and values.(d) [Use Case Diagrams – 5 marks] Draw a Use Case Diagram for a voting machine, onwhich voters can see a list of candidates and select one to vote for. The machine should checkthat each voter is eligible to vote. The electoral registrar will also want to print a summary of thetotal votes for each candidate, and (separately) a list of the voters who have voted, and a list ofthose who haven’t. In case of a dispute, the machine should also list a complete record of whovoted for whom, but only a judge can use this function.VoterJudge<<extends>>ElectoralRegistrar<<uses>>See completeVote recordSee list ofcandidatesVoteCheckeligibilityPrint votesummaryList whovotedList whodidn’t voteNotes: The “extends” link from the judge’s use case isn’t obvious, so don’t penalize if theymissed it.CSC340 Information Systems Analysis and Design page 4/82. [Entity-Relationship Models – 20 marks] The following two alternative Entity-Relationship models have been proposed as the basis for a database to hold information aboutelected presidents and senators in US elections:PersonYear electedPresident Party Senatorstate(0,2) (0,n)(0,1) (0,100) CandidateOfficeheldPartymemberFrom-yearTo-year(0,1)a) [8 marks] An instance of a relationship is a tuple of entity instances (and attribute valueswhere applicable). Write down one example instance for each of the four relationships shownabove. Make up some names if you don’t know any American politicians!President: <George W. Bush, Republican Party, 2004>Senator: <Charles E. Schumer, Democratic Party, 2004, New York>Held: <William J. Clinton, President, 1992, 2000>Member: <John F. Kerry, Democratic Party>b) [4 marks] Give an example of a situation that can be represented in the first model, but notthe second, and an example of a situation that can be represented in the second model but notthe first.The first model allows for the case where a politician changes party between electedoffices, because party is a part of each ‘elected’ relationship. The second model can’tcapture this.The second model copes well with unusual length electoral terms, because the end of theelected period is explicitly represented. E.g. if an elected office was vacant for a year, itwould show up as a gap in the data in the second model, but not in the first. The secondmodel can also accommodate a candidate who is a member of more than one party at once!c) [8 marks] Add multiplicities to both diagrams to show the following constraints. If aconstraint cannot be expressed using multiplicities on one or both models, say so below. i. A person/candidate is either a member of a


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