Презентация «Scheduling. Introduction»

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Scheduling

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Where are we? 1. Introduction 2. Project Life Cycles 3. Project Artifacts 4. Work Elements, Schedule, Budget 4. 1 Work Breakdown Structure 4. 2 Dependencies between tasks - 4. 3 Schedule (Today’s …

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Outline The last lecture dealt with Artifacts of Project Today we focus on Dependencies and Scheduling Estimating times for activities Determining critical path and slack times Determining project …

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Dependency Diagrams (Overview) Dependency diagrams consist of 3 elements Event (also called milestone): A significant occurrence in the life of a project. Activity: Work required to move from one …

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Why Dependency Diagrams? Example: You are assigned a project consisting of 10 activities which take one week each to be completed. How long does the project take? When projects have more than 15-20 …

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1) Activity-on-the-arrow Diagram Notation

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PERT PERT is an activity-on-the-arrow notation PERT = Program Evaluation and Review Technique Developed in the 50s to plan the Polaris weapon system in the USA. PERT allows to assign optimistic, …

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2) Activity-in-the-node Diagram Notation

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Example of an Activity-in -the -Node Diagram

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What do we do with these diagrams? Compute the project duration Determine activities that are critical to ensure a timely delivery Analyse the diagrams to find ways to shorten the project duration To …

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Definitions: Critical Path and Slack Time4 Critical path: A sequence of activities that take the longest time to complete The length of the critical path(s) defines how long your project will take to …

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Example of a critical path

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Definitions: Start and Finish Dates Earliest start date: The earliest date you can start an activity Earliest finish date: The earliest date you can finish an activity Latest start date: The latest …

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2 Ways to Analyze Dependency Diagrams Forward pass: Goal is the determination of critical paths Compute earliest start and finish dates for each activity Start at the beginning of the project and …

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Forward Path Example Activity Earliest Start(ES) Earliest Finish(EF)

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Backward Path Example Activity Latest Start(LS) Latest Finish(LF)

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Computation of slack times Slack time ST of an activity A: STA = LSA - ESA Subtract the earliest start date from the latest start date for each activity

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Path types in dependency graphs Critical path: Any path in a dependency diagram, in which all activities have zero slack time. Noncritical path: Any path with at least one activity that has a nonzero …

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Frequently used formats for dependency graphs Milestone View (“Key-Events report”): A table that lists milestones and the dates on which you plan to reach them. Activities View: A table that lists …

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Key-Events Report Date Milestone August 26 Project Kickoff (with Client) October 16 Analysis Review October 26 System Design Review November 7 Internal Object Design Review November 20 Project Review …

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Activities View Date Project Phases Jul 17-Aug 23 Preplanning Phase Aug 26 - Sep 24 Project Planning Sep 11-Oct 8 Requirements Analysis Oct 9 - Oct 26 System Design Oct 28-Nov 7 Object Design Nov 8 - …

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Gantt Chart

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Gantt Chart

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Two Types of Gantt Charts Person-Centered View To determine people‘s load

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Tools support for Establishing Schedules Tool support for Graphical user interface for entering activity data Automatic computation of critical paths Multiple views (PERT, Gantt, table views) and …

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What do we cover now? How to develop an initial project schedule How to shorten the project duration Mistakes made during preparation of schedules The danger of fudge factors How to identify when a …

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How to develop an Initial Project Schedule Identify all your activities (reuse a template if possible) Identify intermediate and final dates that must be met Assign milestones to these dates Identify …

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Developing a Schedule for Integration Testing Five Steps: 1. Start with System Decomposition 2. Determine your Integration Testing Strategy 3. Determine the Dependency Diagram (UML Activity Diagram) …

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1. Start with System Decomposition

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2. Determine Your Integration Testing Strategy Types of integration testing strategies We choose sandwich testing. Why? It allows many parallel testing activities, possibly shortening testing time …

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Sandwich Testing Sandwich testing combines parallel top-down and bottom-up integration testing Top-down testing tests the top layer incrementally with the components of the target layer Bottom-up …

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3. Determine the Dependency Diagram (Sandwich Testing , UML Activity Diagram)

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Dependency Diagram for a Modified Sandwich Testing Strategy

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4. Add Time Estimates (PERT Chart)

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5. Visualize your Schedule (Gantt Chart View )

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How to reduce the planned project time Recheck the original span time estimates Ask other experts to check the estimates Has the development environment changed? (batch vs interactive systems, …

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Typical Mistakes when Developing Schedules The „Backing in“ Mistake Using Fudge Factors

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The “Backing in” Mistake Definition “Backing In”: You start at the last milestone of the project and work your way back toward the starting milestone, while estimating durations that will add up to …

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Using Fudge Factors Parkinson formulated this law for project completion: Work tends to expand to fill the time allotted for it. Fudge factor: A fudge factor is the extra amount of time you add to …

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Heuristics for dealing with time 1. First Set the Project Start Time => Determines the planned project time Determine the critical path(s) 2. Then try to reduce the planned project time If you …

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Identifying When a Project Goes Off-Track Determine what went wrong: Why is your project got off track? Behind schedule Overspending of resource budgets Not producing the desired deliverables …

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Heuristics to get a project back on track Reaffirm your plan Reaffirm your key people Reaffirm your project objectives Reaffirm the activities remaining to be done Reaffirm roles and responsibilities …

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What makes a Software Project successful? User involvement 20 Support from upper management 15 Clear Business Objectives 15 Experienced Project Manager 15 Shorter project phases („Small milestones“) …

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Become a better software project manager End User and Management involvement 35% Learn how to involve the customer and end users Learn how to get support from your upper management Practice project …

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How to become a better project manager Don’t assume anything Take the time to find out the facts. Use assumptions only as a last resort. With every assumption comes a risk that you are wrong. …

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Additional Readings [IEEE Std 1058] Standard for Software Project Management Plans Stanley E Portny, Project Management for Dummies, Hungry Minds, 2001, ISBN 0-7645-5283-X Standish Group: Chaos, …

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Summary Software Project Management Plan, Section 5: 5. 1 Work Breakdown Structure 5. 2 Dependencies between tasks 5. 3 Resource Requirements (=> Lecture on project organization) 5. 4 Budget …

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Summary: Another view:-) Developing a project plan is is an art. Practice it! Use project templates for yourself or your organization, build these templates iteratively There are several different …

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