I love the sound they make as they fly by. Scheduling Work I love deadlines. I love the sound they make as they fly by. -- Douglas Adams

Software Engineering : A Practitioner’s Approach by Pressman Why is software late? Under-Estimate of effort. Unrealistic deadlines imposed by outsiders. Changing requirements. Risks that were not considered. Technical problems that could not be foreseen. Failure to recognized that the project is falling behind schedule and lack of action to correct the problem. Software Engineering : A Practitioner’s Approach by Pressman

How to build a schedule: Determine dependencies of activities found in WBS. Use dependencies to build activity network diagram (eg PERT). Determine critical path. Map network to a timeline (eg Gantt Chart) using the effort estimates. Use a software tool to help do this work.

Why Determine Dependencies? Dependencies determine deadlines and when work can begin. The WBS shows hierarchy, not dependency. Planners must find all dependencies. Surprises are very bad!

Dependency Types External Dependency Internal Dependency Other projects Stakeholders Sub-Contractors Internal Dependency Audits (design, testing, documentation, …) Sign-Offs at end of phase

Dependency Types FS - T2 cannot start until T1 is finished. Start Finish FS - T2 cannot start until T1 is finished. coding must wait on design to be finished SS - T1 and T2 must start at same time. documentation and coding start together FF - T1 and T2 finish at same time. configuration management ends when coding is done

Dependency Types Lag – T2 cannot start until a given amount of time after T1 is done. Start on-site training one week after final demo to customer management group. Soft – T2 should start after T1, but it is not completely essential that T1 be finished. Populate the new database after the database has been built. If the new database is not completely finished we can still populate the few finished tables.

Activity Networks CPM – Critical Path Method activities are graph nodes (circles) single estimate for duration of tasks PERT – Program Evaluation and Review Technique activities are graph arcs (lines) activity times are ranges and include probabilities

http://www.cs.unc.edu/~stotts/COMP145/homes/map/images/pert.gif

http://www. mckinnonsc. vic. edu http://www.mckinnonsc.vic.edu.au/la/it/ipmnotes/ganttpert/pert_chart.gif

Example Activity Network – Activity on Node 1wks 2wks T5 T2 1wk 3wks 1wk 2wks 1wk T1 T4 T6 T8 T9 4wks T3 3wks T7 Questions: Minimum time to complete the project? Critical Path? Earliest start time, latest start, earliest finish, latest finish? For T2  es=2ndwk ls=4thwk ef=3rdwk lf=5thwk

Resulting Gantt Chart 1 2 3 4 5 6 7 8 9 10 11 12 13 14 T1 T2 T3 T4 T5

Next Time… Making Good PERT charts Managing Uncertainty Resource Leveling Matching to the Calendar and External Resources Correcting Misinterpretations Managing Uncertainty Automated Tools