CS 501: Software EngineeringAdministrationOS 360The Aim of Project ManagementThe Project ManagerProject Planning MethodsTerminologyExample: The Critical Path Method An Open University CourseActivity GraphActivity Graph (part)Activity Graph (continued)Slide 12Scheduling: BackgroundCritical Path MethodTime Estimates for Activities (Weeks)Earliest Start DatesLatest Start DatesCritical PathSlackEstimating the Time for an ActivityStart-up TimeExperience with Critical Path MethodAdding Resources to Activity GraphUsing Critical Path Method for ResourcesKey PersonnelValue of Scheduling ToolsKey Personnel: Schedule for EditorFlexibility: Open University Example1CS 501 Spring 2003CS 501: Software EngineeringLecture 4Project Management2CS 501 Spring 2003AdministrationProjects•New project on Web site: Web Archiving•Announcements by project teams3CS 501 Spring 2003OS 360The operating system for the IBM 360 was two years late.Question: How does a project get two years behind schedule?Answer: One day at a time!Fred Brooks Jr., The Mythical Man Month4CS 501 Spring 2003The Aim of Project ManagementTo complete a project:• On time• On budget• With required functionality• To the satisfaction of the client• Without exhausting the team5CS 501 Spring 2003The Project Manager• Create and maintain the schedule.• Track progress against schedule.• Keep some slack in the schedule (minimize risk).• Continually make adjustments:Start activities before previous activity completeSub-contract activitiesRenegotiate deliverables• Keep senior management informed (visibility).6CS 501 Spring 2003Project Planning MethodsCritical Path Method, Gantt charts, Activity bar charts, etc. are roughly equivalent.These methods are best when:1. Model is updated regularly (e.g., monthly)2. The structure of the project is well understood3. The time estimates are reliable4. Activities do not share resourcesUnfortunately, #2, #3, #4 rarely apply to software development7CS 501 Spring 2003TerminologyDeliverableWork product that is provided to the customer (report, presentation, documentation, code, etc.)ActivityPart of a project that takes place over time.EventThe beginning or end of an activity.MilestoneCompletion of a specified set of activities (e.g., delivery of a deliverable)8CS 501 Spring 2003Example: The Critical Path MethodAn Open University CourseDeliverables:16 Written texts (bound in pairs)8 Television programs8 Radio programs4 Computer programs1 Home experimental kit (scientific calculator)4 Assignments and sample solutions9CS 501 Spring 2003Activity GraphAn activityA dummy activityAn eventA milestone10CS 501 Spring 2003Activity Graph (part)Edit Unit 3PrintUnit 3Revise Unit 3MailUnit 3otheractivitiesSTARTEND11CS 501 Spring 2003Activity Graph (continued)Edit Unit 3TypesetUnit 3Revise Unit 3MailUnits 3/4otheractivitiesEdit Unit 4PrintUnits 3/4Revise Unit 4otheractivitiesTypesetUnit 4START12CS 501 Spring 2003Activity Graph (continued)STARTEdit Unit 3ScriptTV 2MakeTV 2Edit Unit 4Prototype Computer 1ProgramComputer 1DocumentComputer 1Mail13CS 501 Spring 2003Scheduling: BackgroundPERT Program Evaluation and Review Technique introduced by the U.S. Navy in 1957 to support the development of its Polaris submarine missile program.PERT/TimeActivity graph with three time estimates (shortest, most probable, longest) on each activity to compute schedules.PERT/CostAdded scheduling of resources (e.g., facilities, skilled people, etc.)14CS 501 Spring 2003Critical Path MethodUses Activity Graph with single time estimate for each activity to estimate, for each event:earliest start datelatest start dataand for each activity:slackA standard method for managing large construction projects.On big projects, activity graphs with more than 10,000 activities are common.15CS 501 Spring 2003Time Estimates for Activities (Weeks)64223333821 1412121416CS 501 Spring 2003Earliest Start Dates642233338211412121401121241719235252217171515820232417CS 501 Spring 2003Latest Start Dates6 4223333821141212111121413152023 242542201717191018172018CS 501 Spring 2003Critical Path0/01/1112/1212/144/1315/15 17/1717/1717/1719/2022/23 23/2425/2519CS 501 Spring 2003Slack0/01/1117/1723/2412212/1212/144/1315/15 17/1717/17 19/2022/2325/2548123 23124433611Slack of activity = (latest start)end - (earliest start)begin - (time estimate)101000 00009922231111520CS 501 Spring 2003Estimating the Time for an ActivityWith experienced staff, estimating the actual time to carry out a task is usually fairly accurate, but ...The little bits and pieces are underestimated•The time from almost "done" to completely "done" is much longer than anticipated. (There's just one thing to tidy up. I need to put the comments into better shape. I really should get rid of that patch.)•The distractions are not planned for. (My system crashed and I decided to upgrade the software. My child's school was closed because of snow. I spent the day showing visitors around.) Some things have to be done twice.21CS 501 Spring 2003Start-up TimeOn a big project, the start-up time is typically three to six months:• Personnel have to complete previous projects (fatigue) or be recruited.• Hardware and software has to be acquired and installed.• Staff have to learn new domain areas and software (slow while learning).• Clients may not be ready.22CS 501 Spring 2003Experience with Critical Path MethodAdministrative computing department at Dartmouth used the Critical Path Method for implementation phase of major projects.Experience: Elapsed time to complete projects was consistently 25% to 40% longer than predicted by model.Analysis: • Some tasks not anticipated (incomplete understanding)• Some tasks had to be redone (change of requirements, technical changes)• Key personnel on many activities (schedule conflicts)• System ZZZ (non-billable hours)23CS 501 Spring 2003Adding Resources to Activity GraphEach activity is labeled with resources, e.g.,Number of people (e.g., 2 Java programmers)Key personnel (e.g., chief system architect)Equipment (e.g., 3 servers with specified software)Facilities (e.g., video conference center)Each resource is labeled with availability, e.g.,Hiring and trainingVacationsEquipment availability24CS 501 Spring 2003Using Critical Path Method for ResourcesAssume every activity begins at earliest start date:In each time period, calculate:resources requiredresources availableIdentify shortage / surplus
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